CN112913130A

CN112913130A - Voltage supply system and power supply constituting the same

Info

Publication number: CN112913130A
Application number: CN201980070710.2A
Authority: CN
Inventors: 氏丸智彰; 高桥成治; 佐野隆章; 植村匠
Original assignee: Sumitomo Electric Industries Ltd
Current assignee: Sumitomo Electric Industries Ltd
Priority date: 2018-10-26
Filing date: 2019-05-31
Publication date: 2021-06-04
Also published as: JPWO2020084822A1; JP6699804B1; US11502620B2; DE112019005307T5; US20210399650A1; WO2020084822A1

Abstract

Providing: a voltage supply system in which a plurality of power sources (for example, DC-DC converters) are connected in parallel, each power source can be set to an arbitrary load ratio; and a power source. The power supply is in a voltage supply system including a power supply and is connected in parallel with a constant voltage power supply. The power supply outputs a voltage in a constant voltage mode based on a first target voltage. The power supply includes a voltage generation unit outputting a voltage by switching between a constant voltage mode based on a second target voltage greater than the first target voltage and a constant current mode based on a current limit.

Description

Voltage supply system and power supply constituting the same

Technical Field

The present disclosure relates to a voltage supply system and a power supply constituting the same. The present application claims priority from Japanese patent application No.2018-201685, filed on 26.10.2018, the entire contents of which are incorporated herein by reference.

Background

In an electric vehicle or the like, the voltage of a high-voltage battery (e.g., DC 300V) is converted into a low voltage (e.g., DC 14V) by a DC-DC converter to be supplied to a load. In the case where the required current of the load as the voltage supply destination is large, the current capacity using one DC-DC converter may be insufficient. As a measure thereof, it is conceivable to use a plurality of DC-DC converters so as to be connected in parallel.

For example, in the case of using a plurality of DC-DC converters as the same product to be connected in parallel, if the loads (operating conditions) on all the DC-DC converters can be made equal, the lives of the plurality of DC-DC converters can be equalized. However, in practice, even if the DC-DC converters are the same product, each DC-DC converter varies in output voltage. When starting up a DC voltage conversion system having a plurality of DC-DC converters connected in parallel, a DC-DC converter having the largest output voltage among the plurality of DC-DC converters is started up first. Other DC-DC converters cannot perform output because their output voltages are small. During this time, power is supplied to the load only from the DC-DC converter having the maximum output voltage. Then, when the DC-DC converter having the maximum output voltage reaches its own maximum allowable current to limit the current, the DC-DC converter having the second largest output voltage is started. Therefore, since a plurality of DC-DC converters connected in parallel have variations in output voltage, connecting the DC-DC converters in parallel alone cannot equalize their loads. Therefore, there is a problem that a specific DC-DC converter deteriorates earlier than other DC-DC converters, and the life of the DC voltage supply system depends on the life of the specific DC-DC converter.

In order to solve the above problem, patent document 1 discloses a DC voltage conversion device that can prolong the life by equalizing the lives of DC-DC converters connected in parallel. In the DC voltage conversion apparatus, a target value of an output voltage of one of a plurality of DC-DC converters connected in parallel is set to be larger than target values of output voltages of the other DC-DC converters, and a current limit value for limiting an output current of the DC-DC converter is set to be half of a maximum load current. With this configuration, the load is distributed among the plurality of DC-DC converters connected in parallel, so that the lives of the DC-DC converters can be equalized.

CITATION LIST

[ patent document ]

Patent document 1: japanese laid-open patent publication No.2015-144534

Disclosure of Invention

[ problem solution ] to provide a solution

A power supply according to an aspect of the present disclosure is a power supply used in a voltage supply system including a constant voltage power supply configured to output a voltage in a constant voltage mode based on a first target voltage, the power supply being connected in parallel with the constant voltage power supply, the power supply including a voltage generating unit configured to output the voltage in the constant voltage mode based on a second target voltage larger than the first target voltage and in a constant current mode based on a current limit value.

A voltage supply system according to another aspect of the present disclosure is a voltage supply system including: a first power supply configured to output a voltage in a constant voltage mode based on a first target voltage; and a second power supply electrically connected in parallel with the first power supply, wherein the second power supply includes a voltage generating unit configured to output a voltage in a constant voltage mode based on a second target voltage greater than the first target voltage and a constant current mode based on a current limit value.

[ advantageous effects of the invention ]

According to the present disclosure, in a voltage supply system having a plurality of power sources (e.g., DC-DC converters or DC-AC converters) connected in parallel, each power source may be set to a desired load ratio. In addition, according to the present disclosure, it is possible to suppress a variation in the output voltage of the voltage supply system due to a variation in the load current.

Drawings

Fig. 1 is a block diagram showing a configuration of a DC voltage supply system according to an embodiment of the present disclosure.

Fig. 2 is a block diagram illustrating a configuration of the second power supply of fig. 1.

Fig. 3 is a block diagram showing a configuration of the control unit of fig. 1.

Fig. 4 is a flowchart illustrating control of the control unit in the DC voltage supply system of fig. 1.

Fig. 5 is a flowchart illustrating control of the second power supply in the DC voltage supply system of fig. 1.

Fig. 6 is a graph illustrating changes in current and voltage during operation of the DC voltage supply system of fig. 1.

Fig. 7 is a block diagram showing a configuration of a DC voltage supply system according to a first modification.

Fig. 8 is a block diagram illustrating a configuration of the second power supply of fig. 7.

Fig. 9 is a flowchart illustrating control of the second power supply in the DC voltage supply system of fig. 7.

Fig. 10 is a graph illustrating changes in current and voltage during operation of the DC voltage supply system of fig. 7.

Fig. 11 is a block diagram showing a configuration of a DC voltage supply system according to a second modification.

Fig. 12 is a flowchart illustrating control of the control unit in the DC voltage supply system of fig. 11.

Fig. 13 is a flowchart illustrating control of the second power supply in the DC voltage supply system of fig. 11.

Fig. 14 is a graph showing changes in current and voltage during the operation of the DC voltage supply system in fig. 11.

Fig. 15 is a block diagram showing a configuration of an AC voltage supply system according to a second embodiment of the present disclosure.

Fig. 16 is a block diagram showing a configuration of a first power supply of the AC voltage supply system of fig. 15.

Fig. 17 is a block diagram showing a configuration of a second power supply of the AC voltage supply system of fig. 15.

Fig. 18 is a flowchart showing a control structure of a program executed by the internal control circuit of the second power supply of fig. 17.

Fig. 19 is a block diagram showing the configuration of the first power supply in a modification of the second embodiment.

Fig. 20 is a block diagram showing the configuration of an AC voltage supply system according to the third embodiment.

Fig. 21 is a block diagram showing the configuration of the second power supply of the third embodiment.

Fig. 22 is a block diagram showing the configuration of the first power supply of the fourth embodiment.

Fig. 23 is a block diagram showing the configuration of the second power supply of the fourth embodiment.

Detailed Description

[ problem to be solved by the present disclosure ]

There are cases where DC-DC converters having different standard values are connected in parallel. In this case, it is desirable to set a ratio of currents carrying the current to the load (hereinafter, may be referred to as a load ratio) for each of all the DC-DC converters, instead of equalizing the load ratio at each DC-DC converter. In patent document 1, the load ratio of the parallel-connected DC-DC converters cannot be set to a desired value, and therefore the above-described requirements cannot be satisfied.

In addition, the DC voltage conversion device of patent document 1 has a load current region in which only the master converter (DC-DC converter whose output voltage target value is large) operates and load current regions in which the master converter and the slave converter operate, in accordance with a change in the load current. Therefore, there is a problem that a voltage change occurs when switching between the regions. Such a problem is not limited to the case where both the input and output are DC. The same problem occurs, for example, in the case where one or both of the input and output is AC.

Therefore, an object of the present disclosure is to provide a voltage supply system and a power supply that enable each power supply to be set to a desired load ratio in a voltage supply system in which a plurality of power supplies (e.g., DC-DC converters) each performing power conversion are connected in parallel. In addition, an object of the present disclosure is to provide a voltage supply system and a power supply capable of suppressing a variation in output voltage of voltage supply due to a variation in load current in a voltage supply system in which a plurality of power supplies are connected in parallel.

Description of embodiments of the present disclosure

First, the contents of the embodiments of the present disclosure are listed and described. At least some portions of the embodiments described below may be combined as desired.

(1) A power supply according to a first aspect of the present disclosure is a power supply for use in a voltage supply system including a constant voltage power supply configured to output a voltage in a constant voltage mode based on a first target voltage, the power supply being connected in parallel with the constant voltage power supply, the power supply including a voltage generating unit configured to switchably output the voltage between a constant voltage mode based on a second target voltage larger than the first target voltage and a constant current mode based on a current limit value. Therefore, both the power supply and the constant voltage power supply can be operated. By varying the current limit, the power supply and the constant voltage power supply can be operated at a desired load ratio.

(2) Preferably, the power supply further includes a delay unit configured to delay the start of power conversion in the power supply until the constant voltage power supply starts the power conversion. Therefore, the output voltage of the voltage supply system can be determined by the output voltage of the constant voltage power supply. In addition, since the second target voltage is greater than the first target voltage, the power supply starts power conversion after the constant voltage power supply starts power conversion, and thus can operate together with the constant voltage power supply. As a result, a voltage rise in the power supply at the time of startup can be suppressed.

(3) Preferably, the delay unit includes a delay start unit configured to start power conversion in the power supply with a delay of a predetermined period of time after the voltage supply system is started. Therefore, the output voltage of the voltage supply system can be determined by the output voltage of the constant voltage power supply. In addition, since the second target voltage is greater than the first target voltage, the power supply is started after a predetermined period of time, and thus the power supply may operate together with the constant voltage power supply. As a result, a voltage rise in the power supply at the time of startup can be suppressed.

(4) More preferably, the delayed start unit includes: a timer configured to detect that a predetermined period of time has elapsed after the voltage supply system is started; an operation inhibiting unit configured to inhibit an operation of the power supply in response to a fact that the voltage supply system is activated; and an enabling unit configured to disable the operation inhibiting unit and enable power conversion in the power supply in response to a fact that the timer has detected the elapse of the predetermined time period. Since the start-up of the power supply is prohibited until the predetermined period of time elapses after the voltage supply system is started up, the output voltage of the voltage supply system is determined by the output voltage of the constant voltage power supply. In addition, since the second target voltage is greater than the first target voltage, when the inhibition of the start of the power supply is canceled after the predetermined period of time, the power supply starts the power conversion and thus the power supply can operate together with the constant voltage power supply.

(5) Further preferably, the operation prohibiting unit includes a first current setting unit configured to set the current limit value to 0 in response to the fact that the voltage supply system is activated, and the activating unit includes a second current setting unit configured to set the current limit value to a predetermined value larger than 0 in response to the fact that the timer has detected that the predetermined period of time has elapsed. Since the current limit for the power supply is set to 0, no current is output from the power supply and the power supply does not operate during a predetermined period of time from the start of the voltage supply system. When the predetermined period of time has elapsed, the current limit is set to a predetermined value greater than 0. By appropriately setting the predetermined period of time, voltage variation at the time of start-up of the voltage supply system is prevented, and after the predetermined period of time has elapsed, the power supplies operate together with the constant-voltage power supply, so that the respective power supplies can carry load currents.

(6) Preferably, the second current setting unit includes a limit value setting unit configured to set the current limit value at a value between a predetermined lower limit value and an upper limit value, the upper limit value being specified by a current value of the current supplied from the voltage supply system. Since the current output from the second current setting unit is limited between the current value of the voltage supply system and a predetermined lower limit value, the power supplies operate together with the constant voltage power supply, and thus the respective power supplies can carry the load current.

(7) More preferably, the limit value setting unit includes a current limit value determining unit that determines the current limit value as a value obtained by multiplying a current value of the current supplied from the voltage supply system by a value not less than 0 and not more than 1. Therefore, once the power supply has been enabled to operate in the constant current mode, the power supply can be inhibited from operating in the constant voltage mode, so that variations in the voltage supplied from the voltage supply system can be suppressed. In addition, even when the current supplied from the voltage supply system to the load has changed, the set load ratio can be maintained.

(8) It is further preferable that the limit value setting unit includes a setting unit configured to set the current limit value such that a ratio of the current limit value to a current value of the current supplied from the voltage supply system becomes equal to a predetermined target value that is not less than 0 and less than 1. Therefore, once the power supply has started to operate in the constant current mode, the power supply can be inhibited from operating in the constant voltage mode, so that variations in the voltage supplied from the voltage supply system can be suppressed. In addition, even when the current supplied from the voltage supply system to the load has changed, the set load ratio can be maintained.

(9) Further preferably, the second current setting unit includes: a current value receiving unit configured to receive, from the constant voltage power supply, a value indicating a current value of a current output from the constant voltage power supply; and a limit value setting unit configured to set the current limit value such that a ratio of the current limit value to a sum of a current value indicated by the value received by the current value receiving unit and a current value of the current output from the power supply becomes a predetermined target value that is not less than 0 and less than 1. Using a current value of a current output from the constant voltage power supply, the current limit value of the power supply is set such that a ratio of the current limit value to a sum of the current value and an output current value of the power supply becomes a target value of not less than 0 and less than 1. As a result, the power supply carries a part of the current to be supplied from the voltage supply system, and the constant voltage power supply carries the remaining current. An operation in which only one of the power supply and the constant voltage power supply carries current is not performed, and a voltage variation due to the operation can be avoided.

(10) Preferably, the limit value setting unit includes: a current value calculating unit configured to calculate a current value of a current output from the constant voltage power supply by a predetermined conversion expression with respect to the value received by the current value receiving unit; and a current limiting unit configured to set a current limit value such that a ratio of the current limit value to a sum of the current value calculated by the current value calculating unit and an output current value of the power supply becomes a target value. Even in the case where the value received by the receiving unit is not a value directly indicating the current output from the constant voltage power supply, the current output from the constant voltage power supply can be estimated by the current calculating unit performing a predetermined conversion. Based on the estimation result, the current limit value of the power supply is set such that the ratio of the estimated value to the output current value of the power supply becomes a target value of not less than 0 and less than 1. As a result, the power supply carries a part of the current to be supplied from the voltage supply system, and the constant voltage power supply carries the remaining current. An operation in which only one of the power supply and the constant voltage power supply carries current is not performed, and a voltage variation due to the operation can be avoided.

(11) Preferably, the target value is a ratio of a rated output current of the power supply to a sum of the rated output current of the constant voltage power supply and the rated output current of the power supply.

(12) Further preferably, the second target voltage is a value not less than an upper limit of a variation in voltage output from the constant voltage power supply based on the first target voltage. Therefore, the start-up power supply can be ensured. As a result, both the DC power supply and the constant voltage power supply can be easily operated.

(13) Preferably, the second target voltage is a value equal to an upper limit of a variation in voltage output from the constant voltage power supply based on the first target voltage. Thus, the power supply can be started. As a result, both the power supply and the constant voltage power supply can be easily operated. In addition, an increase in the output voltage of the voltage supply system caused when the load current has become less than the current limit value can be minimized.

(14) The variation is a value determined by the specification of the constant voltage power supply. The current limit can be easily set by using the specifications of the constant voltage power supply. As a result, both the power supply and the constant voltage power supply can be easily operated. It is possible to minimize the variation of the output voltage of the voltage supply system caused when the load current has become smaller than the current limit value.

(15) More preferably, the power supply further includes a current value receiving unit configured to receive a signal indicating a current value of the current supplied from the voltage supply system, wherein the second current setting unit includes a current limit value setting unit configured to set the current limit value to a value between a predetermined lower limit value and the current value indicated by the signal received by the current value receiving unit. Since the current limit value can be made smaller than the current value of the current supplied from the voltage supply system, the current value of the current supplied from the voltage supply system can be divided between the constant-voltage power supply and the power supply. As a result, a state where only the power supply carries current does not occur, and a voltage variation from the output voltage of the constant voltage power supply to the output voltage of the power supply can be prevented from occurring.

(16) Further preferably, the power supply further includes a current sensor configured to detect a current value of the current supplied from the voltage supply system to the load, wherein the current value receiving unit receives a signal indicating the current value from the current sensor. Since the current limit value can be made smaller than the current value of the current supplied from the voltage supply system, the current value of the current supplied from the voltage supply system can be divided between the constant-voltage power supply and the power supply. As a result, a state where only the power supply carries current does not occur, and a voltage variation from the output voltage of the constant voltage power supply to the output voltage of the power supply can be prevented from occurring.

(17) Preferably, the voltage supply system further comprises: a current sensor configured to measure a current value of a current supplied from the voltage supply system to a load; and a control unit configured to supply a signal indicating the current value measured by the current sensor to the current value receiving unit, and the current value receiving unit receives the signal from the control unit. Since the current limit value can be made smaller than the current value of the current supplied from the voltage supply system, the current value of the current supplied from the voltage supply system can be divided between the constant-voltage power supply and the power supply. As a result, a state where only the power supply carries current does not occur, and a voltage variation from the output voltage of the constant voltage power supply to the output voltage of the power supply can be prevented from occurring.

(18) More preferably, the power supply further includes a current value receiving unit configured to receive a current value of the current output from the constant voltage power supply, wherein the second current setting unit includes a current limit value setting unit configured to set the current limit value such that a ratio of the current limit value to the current value received by the current value receiving unit becomes a predetermined target value. Since the current limit value can be made smaller than the current value of the current supplied from the voltage supply system, the current value of the current supplied from the voltage supply system can be divided between the constant-voltage power supply and the power supply. As a result, a state where only the power supply carries current does not occur, and a voltage variation from the output voltage of the constant voltage power supply to the output voltage of the power supply can be prevented from occurring.

(19) Further preferably, the voltage supply system further includes: a current sensor configured to measure a current value of a current output from the constant voltage power supply; and a control unit configured to output a signal indicating a current value measured by the current sensor, wherein the current value receiving unit receives the signal from the control unit. Since the current limit value can be made smaller than the current value of the current supplied from the voltage supply system, the current value of the current supplied from the voltage supply system can be divided between the constant-voltage power supply and the power supply. As a result, a state where only the power supply carries current does not occur, and a voltage variation from the output voltage of the constant voltage power supply to the output voltage of the power supply can be prevented from occurring.

(20) Preferably, the power supply further includes a current sensor configured to measure a current value of the current output from the constant voltage power supply, wherein the current value receiving unit receives the current value from the current sensor. Since the current limit value can be determined based on the current value of the current output from the constant voltage power supply, the current value of the current supplied from the voltage supply system can be distributed between the constant voltage power supply and the power supply. As a result, a state where only the power supply carries current does not occur, and a voltage variation from the output voltage of the constant voltage power supply to the output voltage of the power supply can be prevented from occurring.

(21) More preferably, the operation prohibiting unit includes a drive signal stopping unit configured to stop outputting the drive signal to the voltage generating unit in response to a fact that the voltage supply system is activated, and the activating unit includes a drive signal outputting unit configured to start outputting the drive signal to the voltage generating unit in response to a fact that the timer has detected that the predetermined period of time has elapsed. The driving signal to the voltage generating unit is stopped until a predetermined time elapses, and then the voltage generating unit is driven to start power conversion. Therefore, both the power supply and the constant voltage power supply can be operated. By changing the current limit, the power supply and the constant voltage power supply can be operated at a desired load ratio.

(22) Further preferably, the delayed start unit includes: a timer configured to detect that a predetermined period of time has elapsed after the voltage supply system is started; a drive signal output stopping unit configured to stop outputting the drive signal to the voltage generating unit in response to a fact that the voltage supply system is activated; and a starting unit configured to start power conversion in the power supply by disabling the driving signal output stopping unit in response to a fact that the timer detects that the predetermined period of time has elapsed. The driving signal to the voltage generating unit is stopped until a predetermined period of time elapses, after which the voltage generating unit is driven to start power conversion. Therefore, both the power supply and the constant voltage power supply can be operated. By changing the current limit, the power supply and the constant voltage power supply can be operated at a desired load ratio.

(23) Preferably, the delay unit includes a delay start-up unit configured to start up power conversion in the power supply in response to the fact that the power conversion in the constant voltage power supply is started up. After the power conversion in the constant voltage power supply is started, the power conversion in the power supply is started. Therefore, the power supply can also be started, so that both the power supply and the constant voltage power supply can be operated. By changing the current limit, the power supply and the constant voltage power supply can be operated at a desired load ratio.

(24) More preferably, the delay start unit starts the power conversion in the power supply in response to at least one of a fact that the output voltage of the constant voltage power supply has reached the first target voltage and a fact that information indicating that the power conversion is started is received from the constant voltage power supply. When the constant voltage power supply has started power conversion, the output voltage reaches the first target voltage. In addition, information indicating that the constant voltage power supply has started power conversion may be received from the constant voltage power supply. In any case, after the power conversion in the constant voltage power supply is started, the power conversion in the power supply is started. Therefore, the power supply can also be started, so that both the power supply and the constant voltage power supply can be operated. By changing the current limit, the power supply and the constant voltage power supply can be operated at a desired load ratio.

(25) More preferably, the power supply further includes a target voltage replacing unit configured to replace the second target voltage with the voltage output from the power supply in response to the fact that the voltage generating unit has started to output the voltage in the constant current mode after the voltage supply system is started up. Therefore, the amplitude of variation in the voltage supplied from the voltage supply system caused by the power supply operating in the constant voltage mode can be further reduced.

(26) Further preferably, the power supply further comprises: a state detection unit configured to detect an operation state of the power supply; and a limiting unit configured to limit an operation of the power supply in response to a fact that the state detecting unit has detected that the power supply is operating in the constant voltage mode. The fact that the power supply operates in a constant voltage mode means that the constant voltage power supply does not output a current. In this case, by limiting the operation of the power supply, the constant-voltage power supply can be operated together with the power supply, and the variation width of the voltage supplied from the voltage supply system can be reduced.

(27) Preferably, the state detection unit detects whether the power supply is operating in the constant voltage mode based on whether the output voltage of the power supply has reached the second target voltage. The fact that the output voltage of the power supply has reached the second target voltage means that the power supply operates in a constant voltage mode. This means that the constant voltage power supply does not output a current. In this case, by limiting the operation of the power supply, the constant-voltage power supply can be operated together with the power supply, and the variation width of the voltage supplied from the voltage supply system can be reduced.

(28) More preferably, the limiting unit reduces the current limit value to a value not less than 0 in response to the fact that the state detecting unit has detected that the power supply is operating in the constant voltage mode. Thus, the power supply can remain operating in the constant current mode even if the load current has changed sharply to be less than the current limit. As a result, an increase in the output voltage of the voltage supply system can be suppressed.

(29) Preferably, the power supply further comprises a measuring unit configured to measure the output current of the power supply, wherein the current limit value is reduced to a value not less than 0 in response to the fact that the output current measured by the measuring unit has become less than the current limit value. Thus, the power supply can remain operating in the constant current mode even if the load current has changed sharply to be less than the current limit. As a result, an increase in the output voltage of the voltage supply system can be suppressed.

(30) More preferably, the power supply further includes a determination unit configured to determine whether the constant voltage power supply is stopped, and in response to the fact that the determination unit has determined that the constant voltage power supply is stopped, the power supply replaces the second target voltage with the first target voltage and replaces the current limit with a rated maximum current value of the power supply. Therefore, even when the constant voltage power supply is stopped, an increase in the output voltage of the voltage supply system can be suppressed.

(31) Preferably, the constant voltage power supply includes a DC constant voltage power supply configured to output a DC voltage in a constant voltage mode based on a first target voltage, and the power supply includes a DC voltage generating unit configured to switchably output the DC voltage between a constant voltage mode based on a second target voltage greater than the first target voltage and a constant current mode based on a current limit value. Both the DC power supply and the DC constant voltage power supply can be operated. By changing the current limit value, the DC power supply and the DC constant voltage power supply can be operated at a desired load ratio to output the load current.

(32) More preferably, the constant voltage power supply includes an AC constant voltage power supply configured to output an AC voltage in a constant voltage mode based on a first target voltage, and the power supply includes an AC voltage generating unit configured to switchably output the AC voltage between a constant voltage mode based on a second target voltage greater than the first target voltage and a constant current mode based on a current limit value. Both an AC power supply and an AC constant voltage power supply can be operated. By changing the current limit value, the AC power supply and the AC constant voltage power supply can be operated at a desired load ratio to output a load current.

(33) The DC voltage supply system according to the second aspect of the present disclosure includes: a first power supply configured to output a voltage in a constant voltage mode based on a first target voltage; and a second power supply connected in parallel with the first power supply, wherein the second power supply includes a voltage generating unit configured to switchably output a voltage between a constant voltage mode based on a second target voltage greater than the first target voltage and a constant voltage mode based on a current limit value. Thus, both the first power supply and the second power supply may be operated. Further, by changing the predetermined value, the first power supply and the second power supply can be operated at a desired load ratio.

Details of embodiments of the present disclosure

In the following embodiments, like parts are denoted by like reference numerals. The names and functions of these components are also the same. Therefore, detailed description of those components will not be repeated.

(first embodiment)

[ INTEGRAL CONFIGURATION ]

Referring to fig. 1, a DC voltage supply system 100 according to a first embodiment of the present disclosure includes a battery 102, a first power source 104, a second power source 106, and a control unit 108. The DC voltage supply system 100 is used for, for example, an electric vehicle or the like, and supplies a constant DC voltage to a load 110. The battery 102 is a battery (e.g., a secondary battery) that supplies a high voltage (e.g., 300V). The first power supply 104 and the second power supply 106 are connected in parallel. That is, the positive input terminals of the first power supply 104 and the second power supply 106 are connected to each other, and the positive output terminals of the first power supply 104 and the second power supply 106 are connected to each other. The parasitic resistance 112 and the parasitic resistance 114 represent substantial resistance on the trace (resistance of the wire, resistance of the connection portion, etc.). As used herein, "connected" refers to an electrical connection.

The positive terminal of the battery 102 is connected to the commonly connected positive input terminal of the first power source 104 and the second power source 106. The commonly connected positive output terminals of the first power source 104 and the second power source 106 form a connection node 116 as a voltage supply terminal from the DC voltage supply system 100 to the load 110. The negative side of each component is grounded.

When the output current of the first power supply 104 (value I1) flows through the parasitic resistance 112, a voltage drop of I1 × R1 occurs. Similarly, when the output current of the second power supply 106 (value I2) flows through the parasitic resistance 114, a voltage drop of I2 × R2 occurs. The voltage VL at the connection node 116 becomes a value smaller than the output voltage V1 of the first power supply 104 by the voltage drop of I1 × R1. In addition, the output voltage VL becomes a value smaller than the output voltage V2 of the second power supply 106 by a voltage drop of I2 × R2. These two values are equal to each other, and thus the following expression is satisfied.

VL＝V1-I1×R1＝V2-I2×R2

The current value IL of the current supplied from the DC voltage supply system 100 is the sum of the output current value I1 of the first power supply 104 and the output current value I2 of the second power supply 106 (IL ═ I1+ I2).

The first power supply 104 and the second power supply 106 are DC-DC converters. The first power supply 104 and the second power supply 106 convert the DC voltage input from the battery 102 into predetermined output voltages V1 and V2, respectively, and output voltages V1 and V2 from output terminals. The first power supply 104 operates by Constant Voltage (CV) control to output a specified constant output voltage V1 (hereinafter, may be referred to as a constant voltage mode). The second power supply 106 operates by Constant Voltage Constant Current (CVCC) control, and therefore, in addition to operating in the constant voltage mode, the second power supply 106 can perform output at a specified constant current value I2 (hereinafter, may be referred to as constant current mode) by Constant Current (CC) control, that is, the second power supply 106 can switchably operate between the constant voltage mode and the constant current mode.

Referring to fig. 2, the second power supply 106 includes: a DC-DC unit 150, the DC-DC unit 150 being switchably operable between a target value based on the output voltage in the constant voltage mode (hereinafter, referred to as a second target voltage, which is greater than the target value of the output voltage of the first power supply 104 (hereinafter, referred to as a "first target voltage")) and a constant current mode based on a current limit value; a power supply internal control unit 152; and an IF unit 154. The DC-DC unit 150 functions as a voltage generating unit for generating an output voltage of the second power supply 106, and as described above, operates in the constant voltage mode or the constant current mode by CVCC control, converts a DC voltage input from the battery 102 into a predetermined voltage, and outputs the converted voltage to the connection node 116. The IF unit 154 receives data transmitted from the control unit 108 and inputs the data to the power supply internal control unit 152. The power supply internal control unit 152 is, for example, a microcomputer including an internal memory. The internal memory stores therein a program to be executed by the power supply internal control unit 152, necessary parameters, and the like. The power supply internal control unit 152 calculates a setting value required for the operation of the DC-DC unit 150 based on data received from the IF unit 154, and sets the setting value for the DC-DC unit 150.

Referring to fig. 3, the control unit 108 includes a Central Processing Unit (CPU)120, a memory 122, an interface unit (hereinafter, referred to as an IF unit) 124, and a bus 126. Data transfer between the components is performed via the bus 126. The memory 122 is, for example, a rewritable semiconductor nonvolatile memory or the like. The memory 122 stores therein programs to be executed by the CPU 120, predetermined parameters, and the like. When the CPU 120 executes the program, a part of the area of the memory 122 is used as a work area. The control unit 108 is, for example, an Electronic Control Unit (ECU) of an electric vehicle or the like.

The CPU 120 controls the operation of the first power supply 104 and the second power supply 106. That is, the CPU 120 transmits the first target voltage to the first power supply 104 via the IF unit 124. Further, the CPU 120 transmits the second target voltage and a limit value for the output current in the constant current mode (hereinafter, referred to as a current limit value) to the second power supply 106 via the IF unit 124. Therefore, as described above, the first power supply 104 operates in the constant voltage mode to output a voltage equal to the first target voltage. In addition, as described above, when operating in the constant current mode, the second power supply 106 outputs a current equal to the current limit, and when operating in the constant voltage mode, the second power supply 106 outputs a voltage equal to the second target voltage.

Operation of DC Voltage supply System

Referring to fig. 4 and 5, a voltage supply operation of the DC voltage supply system 100 will be described. The processing shown in fig. 4 is realized by the CPU 120 reading a predetermined program from the memory 122 and executing the program.

In step 300, a target voltage for the first power supply 104 is transmitted. Specifically, the CPU 120 reads a first target voltage specified for the first power supply 104 from the memory 122, and transmits the first target voltage to the first power supply 104 and the second power supply 106 via the IF unit 124. For example, the first power supply 104 and the second power supply 106 each store the received first target voltage in an internal memory.

In step 302, the load current value is transmitted. Specifically, the CPU 120 transmits a current value of a current to be supplied from the DC voltage supply system 100 to the load 110 to the second power supply 106.

In step 304, the supply of voltage to the load 110 is started. For example, the CPU 120 transmits a start instruction for starting output to the first power supply 104 and the second power supply 106 via the IF unit 124, thereby starting supply of electric power from the output terminals of the first power supply 104 and the second power supply 106.

In step 306, it is determined whether an instruction to stop the DC voltage supply system 100 is received. The stop instruction is executed by, for example, turning off the equipment (electric vehicle, etc.) in which the DC voltage supply system 100 is installed. If it is determined that a stop instruction is received, control proceeds to step 308. Otherwise, step 306 is repeated.

In step 308, a stop process is performed. For example, the CPU 120 sends a stop instruction to the first power supply 104 and the second power supply 106 via the IF unit 124 to stop the output. Then, the routine ends.

The processing shown in fig. 5 is realized by the power supply internal control unit 152 reading a predetermined program from the internal memory and executing the program. Here, it is assumed that the power supply internal control unit 152 has received the first target voltage, the load current value, and the start instruction transmitted from the control unit 108 via the IF unit 154 as described above.

In step 400, a second target voltage is set. Specifically, the power supply internal control unit 152 determines a second target voltage from the first target voltage, and sets the second target voltage for the DC-DC unit 150. The second target voltage is set to be slightly greater than the first target voltage (both the first target voltage and the second target voltage are positive values).

In the present embodiment, the second power supply 106 needs to be started with a delay with respect to the start of power conversion in the first power supply 104. Therefore, in step 402, the power supply internal control unit 152 sets 0A (zero amperes) to the current limit of the DC-DC unit 150 to disable the operation of the DC-DC unit 150 and enable the voltage output. Since the current limit is set to 0, the second power supply 106 does not operate and power is supplied to the load 110 by the first power supply 104. That is, a voltage equal to the first target voltage is output from the first power source 104, and a current is supplied to the load 110. The current required by the load 110 is all supplied from the first power source 104. In the present embodiment, the operation of the DC-DC unit 150 is prohibited by setting 0A as the current limit value. However, the present disclosure is not limited to such embodiments. For example, when the power supply internal control unit 152 performs a process of calculating a signal value for driving the DC-DC unit 150 by Pulse Width Modulation (PWM), a PWM signal as a driving signal thereof may not be output to the DC-DC unit 150.

In step 404, the power supply internal control unit 152 determines whether a predetermined period of time has elapsed since the output voltage was started. If it is determined that the predetermined period of time has elapsed, control proceeds to step 406. Otherwise, step 404 is repeated. The power supply internal control unit 152 may determine that the time period has elapsed by using a timer in the case of having the timer, or may determine that the time period has elapsed by counting an operation clock in the case of not having the timer.

In step 406, the power supply internal control unit 152 determines a current limit value greater than 0 from the load current value received from the control unit 108 and sets the current limit value for the DC-DC unit 150. The current limit is set according to a load ratio of the first power source and the second power source. Therefore, the current supply from the second power source 106 to the load 110 is started, and therefore, the current value I1 of the current supplied from the first power source 104 to the load 110 decreases. The current value I2 of the current supplied from the second power supply 106 is limited to the current limit value, and therefore, after increasing to the current limit value, the current value I2 becomes a value equal to the current limit value. Therefore, the current value I1 of the current supplied from the first power supply 104 to the load 110 becomes a value obtained by subtracting the current limit value of the second power supply 106 from the current value IL of the current flowing through the load 110.

In step 408, the power supply internal control unit 152 determines whether a stop instruction is received from the control unit 108. If it is determined that a stop instruction is received, control proceeds to step 410. Otherwise, step 408 is repeated.

In step 410, the power supply internal control unit 152 stops the DC-DC unit 150.

As described above, in the DC voltage supply system 100, both the first power supply 104 and the second power supply 106 can be operated. As a result, load concentration in which current is supplied to the load 110 from only one power source can be prevented, and current supply to the load 110 can be distributed between two power sources.

Referring to fig. 6, the change of voltage and current in the DC voltage supply system 100 under the above control will be described. The uppermost graph shows a current value IL of a current supplied from the DC voltage supply system 100 and flowing to the load 110. Here, it is assumed that the current originally required by the load 110 (the load current value transmitted in step 302) is 100A. The curves for the second and third stages show the change in output current (I1 and I2) of the first and

second power sources

104 and 106, respectively. The graph of the lowest stage shows the output voltage VL of the DC voltage supply system 100. In the lowest-order graph, the first and second target voltages, which are the target voltages of the first and second power supplies 104 and 106 (i.e., the output voltages of the first and second power supplies 104 and 106), are indicated by broken lines. Here, it is assumed that the first target voltage is set to 14.2V and the second target voltage is set to 15.0V. In addition, the ratio of the current to be supplied to the load 110 is set to the first power supply: second power supply ═ 4: 1, as a target.

As described above, the voltage supply from the DC voltage supply system 100 is started (step 304). Since the current limit for the second power supply 106 is set to 0, no current is supplied from the second power supply 106. A voltage equal to the first target voltage is output from the first power supply 104. The current required by the load 110 is supplied by the first power source 104. That is, during the period from 0 to t0 in fig. 6, the current value IL of the load 110 is equal to the output current value I1 of the first power supply 104. The current value IL increases to a current value (100A) initially required by the load 110 and then becomes stable. That is, at this point of time, the voltage supply from the first power supply 104 is started. At this time, the voltage VL supplied to the load 110 is determined by the output voltage V1 of the first power supply 104 operating in the constant voltage mode. During the period from 0 to t0, as the output current value I1 of the first power supply 104 increases, the voltage drop caused by the parasitic resistance 112 also increases. Accordingly, the output voltage VL of the DC voltage supply system 100 is decreased from the first target voltage. During the period from t0 to t2, the ratio of the output current value I1 of the first power supply 104 is 100% (I1 ═ IL). As a result, the voltage drop caused by the parasitic resistance 112 is slightly larger than that when the ratio of the output current value I1 of the first power supply 104 is the target ratio (80%). Therefore, when the ratio of the currents supplied from the first power supply 104 and the second power supply 106 to the load 110 becomes equal to the target (first power supply: second power supply ═ 4: 1), the voltage VL becomes stable at a value slightly smaller than the voltage (assumed here to be 14.0V), and the DC voltage supply system 100 becomes stable.

After the predetermined short period of time has elapsed (t 1 in FIG. 6), the current limit of the second power supply 106 is altered to a value greater than 0 (step 308). As a result, the current value I2 is output from the second power supply 106, and the current value I2 increases to the current limit value. Here, the current limit is set to 20A. After the current supply from the second power source 106 to the load 110 is started, the current value I2 increases for a period from t1 to t 2. During this period, the current value IL of the current flowing to the load 110 is constant, and thus the output current value I1 of the first power supply 104 is reduced. After the output current value I2 of the second power supply 106 becomes the current limit value (20A), the current value I2 of the second power supply 106 becomes constant (20A) (during the period from t2 to t 3). Therefore, the output current value I1 of the first power supply 104 also becomes constant. Here, the current limit of the second power supply 106 is set to 20A. Therefore, if IL is 100(a), I1 is 100-20 ═ 80(a), and the output voltage VL of the DC voltage supply system 100 becomes 14.0V as described above.

The current value IL of the current flowing to the load 110 may vary. For example, it is assumed that the DC voltage supply system 100 is mounted on an electric vehicle. In this case, the current flowing to the electrical equipment constituting the load 110 varies depending on the state of the electric vehicle (stopped state, running state, ignition state, etc.). For example, it is assumed that the current value IL of the current flowing to the load 110 varies as shown by a rectangle 200 in fig. 6. Even in this case, if IL ≧ current limit is satisfied, the output current value I2 of the second power supply 106 remains at the current limit (20A), and the second power supply 106 remains operating in constant-current mode. The variation in the current value IL of the current flowing to the load 110 during the period from t3 to t4 (variation in the output current value I1) is solved by the first power source 104. When the output current value I1 of the first power supply 104 changes, the voltage drop due to the parasitic resistance 112 changes. Therefore, as shown in fig. 6, the output voltage VL of the DC voltage supply system 100 changes. However, the influence of the voltage drop is small, and therefore the output voltage VL of the DC voltage supply system 100 is kept at a substantially constant value.

In the above description, the current limit value of the second power supply 106 is set so that, of the total current (100A) of the load 110, 20A (20%) of the current is supplied from the second power supply 106 and the remaining current 80A (80%) is supplied from the first power supply 104. However, the current limit when the second power supply 106 operates in the constant current mode may be changed. Therefore, the load ratio of the current value IL at which the first power source 104 and the second power source 106 carry the current to the load 110 can be freely set. The set load ratio can be maintained even if the current supplied from the DC voltage supply system 100 to the load 110 is changed. For example, the current limit may be determined to be a desired value that is less than a specified current value that is a predicted value of the current to be supplied from the DC voltage supply system 100 to the load 110. In this case, the predicted value is, for example, a predicted average value, a predicted maximum value, or the like. If the current limit is set to 1/5 for the specified current value, the load ratio may be the first power supply: second power supply ═ 4: 1. if the current limit is set to 2/5 for the specified current value, the load ratio may be the first power supply: second power supply — 3: 2.

even if the target value of the output voltage is constant, the output voltage of the power supply varies. Therefore, in consideration of the variation of the output voltage of the first power supply 104, it is preferable that the second target voltage is set to be not less than the upper limit value of the variation of the voltage from the output of the first power supply 104 based on the set first output voltage. Accordingly, the second power source 106 can be activated, and a state in which only the first power source 104 supplies current to the load 110 and the load concentrates only on the first power source 104 can be avoided. The variations include variations caused by the power supply itself and variations caused by the parasitic resistance 112. Regarding this variation, the output voltages of a large number of products are statistically processed under the same conditions, and are set based on the obtained distribution. That is, in a case where it is assumed that the distribution of the output voltage conforms to a normal distribution, for example, a value obtained by adding 3 σ (σ is a standard deviation) to the average value of the output voltage is used as the upper limit value. Therefore, the output voltage becomes a value smaller than the upper limit value with a certain probability. In practice, these values constitute some nominal values of the DC-DC unit. That is, in the present embodiment, the upper limit value indicated by the rated value of the DC-DC unit may be used as the upper limit value of the variation.

In fig. 6, even when the current value IL of the current flowing to the load 110 is reduced so that the current value IL becomes equal to the current limit value (as indicated by a circle 202), the second power supply 106 operates in the constant current mode, and the output current value I2 is maintained at the current limit value (20A). However, the output current value I1 of the first power supply 104 becomes 0 (time t5 in fig. 6). When the current value IL of the current flowing to the load 110 further decreases so that the current value IL becomes smaller than the current limit value, the output current value I2 of the second power supply 106 becomes smaller than the current limit value (20A). As a result, the second power supply 106 starts operating in the constant voltage mode (during the period from t5 to t6 in fig. 6). Therefore, the voltage VL supplied to the load 110 is determined by the output voltage V2 (i.e., the second target voltage) of the second power supply 106. The output voltage VL of the DC voltage supply system 100 becomes a value smaller than the output voltage V2 of the second power supply 106 by a voltage drop due to the parasitic resistance 114. That is, the following expression is satisfied.

VL＝V2-I2×R2

However, the second target voltage is greater than the first target voltage, and the voltage drop due to the parasitic resistance 114 is small. Therefore, the voltage VL supplied to the load 110 becomes larger than that in the state where IL > the current limit value. In fig. 6, this voltage difference is represented by Δ V1. Thereafter, when the current value IL returns to greater than the current limit, the second power supply 106 operates in a constant current mode. The output current value I2 is held at the current limit value (20A). The output current value I1 of the first power supply 104 becomes greater than 0. As described above, the output voltage VL of the DC voltage supply system 100 is determined by the output voltage V1 (first target voltage) of the first power supply 104, and thus the output voltage VL returns to 14.0 (V).

Therefore, in order to suppress a variation in the output voltage VL of the DC voltage supply system 100 in the case where the current value IL becomes smaller than the current limit value (during the period of t5 to t6 in fig. 6), it is preferable that the second target voltage be set to be larger than the first target voltage and as small as possible. As described above, even if the target value of the output voltage is constant, the output voltage of the power supply varies. In view of this variation, it is preferable to set the second target voltage to an upper limit value of the variation of the voltage output from the first power supply 104 based on the set first output voltage or a value as close to the upper limit value as possible. Examples of methods for determining the upper limit value of the variation are described above.

(first modification)

As described above, in the DC voltage supply system 100, during the period from t5 to t6 in fig. 6, the second power supply 106 operates in the constant voltage mode, so that the output voltage VL changes (increases). A configuration for suppressing a change will be described as a first modification. In this modification, when the DC voltage supply system has become stable, the second target voltage set for the second power supply 106 is replaced with the actual output voltage value of the second power supply 106.

Referring to fig. 7, a DC voltage supply system 130 according to the first modification has the same configuration as the DC voltage supply system 100 shown in fig. 1, but the internal configuration of a second power supply 132 is different from that of the second power supply 106 in fig. 1.

Referring to fig. 8, the second power supply 132 includes a DC-DC unit 150, a power supply internal control unit 152, an IF unit 154, and a voltmeter 134. The DC-DC unit 150, the power supply internal control unit 152 and the IF unit 154 function in the manner described with respect to the second power supply 106 in fig. 1. The voltmeter 134 measures the output voltage V2 of the second power supply 132. The measured voltage value is input to the power supply internal control unit 152. The voltmeter 134 is, for example, a voltage sensor. If the output signal (measured value) from the voltmeter 134 is a digital signal (digital data), the power supply internal control unit 152 receives the digital data as it is and stores the digital data in the internal memory. If the output signal from the voltmeter 134 is an analog signal, the power supply internal control unit 152 may be provided with an a/D converter to sample the signal and convert the signal into digital data.

Referring to fig. 9, a voltage supply operation of the DC voltage supply system 130 will be described.

Fig. 9 is a flow chart in which a new step 420 is added between step 406 and step 408 in the flow chart of fig. 5. The processing shown in fig. 9 is realized by the power supply internal control unit 152 reading a predetermined program from the internal memory and executing the program.

As described above, through steps 400 to 406, if the output current value IL of the DC voltage supply system 130 is greater than the current limit value, the second power supply 106 operates in the constant current mode to output a current equal to the set current limit value, and the remaining current of the current value IL of the current flowing to the load 110 is supplied from the first power supply 104.

In step 420, the power supply internal control unit 152 changes the current target voltage (second target voltage) of the second power supply 132 to the measured value of the output voltage of the second power supply 132. Specifically, the power supply internal control unit 152 acquires the output voltage of the second power supply 132 measured by the voltmeter 134 and sets the value thereof as the second target voltage of the DC-DC unit 150. That is, the second target voltage (hereinafter, may be referred to as an initial target voltage) received from the control unit 108 and set for the DC-DC unit 150 is changed to a new second target voltage (a measured value of the output voltage of the second power supply 132) in step 400.

Thereafter, the voltage supply from the DC voltage supply system 130 to the load 110 is performed until it is determined in step 408 that the stop instruction is received.

If the DC voltage supply system 130 is stable, the second power supply 132 is operating in the constant current mode, and the output current value I2 is equal to the current limit value, the output voltage VL of the DC voltage supply system 130 is determined by the output voltage of the first power supply 104 operating in the constant voltage mode. The output voltage V2 of the second power supply 132 and the output voltage VL of the DC voltage supply system 130 satisfy the relationship of V2 ═ VL + I2 × R2. Generally, the parasitic resistance is small, and therefore, the voltage drop (I2 × R2) due to the parasitic resistance 114 is small, so that the output voltage V2 of the second power supply 132 is slightly larger than the output voltage VL. The parasitic resistance 112 and the parasitic resistance 114 may be considered to be values approximately equal to each other, and the output voltage V2 of the second power supply 132 operating in the constant current mode is a value close to the first target voltage. That is, when the second power supply 132 operates in the constant current mode, the output voltage V2 measured by the voltmeter 134 is smaller than the initial target voltage (a value larger than the first target voltage) of the second target voltage set for the second power supply 132.

Also in the DC voltage supply system 130, as in the case shown in fig. 6 regarding the DC voltage supply system 100 (the period from t5 to t 6), when the second power supply 132 operates in the constant voltage mode (I2< current limit), the output current value I1 of the first power supply 104 becomes 0. The output voltage VL of the DC voltage supply system 130 is determined by the output voltage V2 of the second power supply 132 operating in a constant voltage mode. However, in the DC voltage supply system 130, unlike the DC voltage supply system 100, the second target voltage set for the second power supply 132 is replaced with the measured output voltage V2 as described above. Therefore, the variation of the output voltage VL of the DC voltage supply system 130 can be made smaller than the variation of the output voltage VL of the DC voltage supply system 100.

Referring to fig. 10, a more detailed description will be given. The graph in fig. 10 shows the changes in current and voltage in the case where the output current value IL of the DC voltage supply system 130 is changed in the same manner as in fig. 6. Fig. 10 differs from fig. 6 only in the graph at the lowest stage.

In fig. 10, the process in step 420 is performed at time t 7. That is, as indicated by the circle 204, the second target voltage of the second power supply 132 is changed to the measured value of the output voltage V2 of the second power supply 132, so that the second target voltage is lowered. Otherwise, the changes in current and voltage during the period from 0 to t5 are the same as in fig. 6. During the time period from t7 to t5, the second target voltage is different from the value in fig. 6, but the second power supply 132 operates in a constant current mode. The output voltage VL of the DC voltage supply system 130 is determined by the output voltage V1 (i.e., the first target voltage) of the first power supply 104, and therefore, the output voltage VL varies in the same manner as fig. 6. Thereafter, during a period from t5 to t6, the output current value IL of the DC voltage supply system 130 decreases. When the output current value IL has become smaller than the current limit value, the output voltage VL of the DC voltage supply system 130 is determined by the output voltage (second target voltage) V2 of the second power supply 132, and thus becomes a value close to the output voltage V2 of the second power supply 132. In the DC voltage supply system 130, after time t7, the second target voltage is set to be less than the initial target voltage. As a result, the variation in the output voltage VL of the DC voltage supply system 130 (represented by Δ V2 in fig. 10) becomes smaller as compared with the case where the second target voltage is maintained at the initial target voltage (fig. 6).

In a state where the DC voltage supply system 130 is stable, the second power supply 132 operates in the constant current mode, and the output current value I2 is equal to the current limit value, the output voltage of the second power supply 132 is measured. The second target voltage (initial target voltage) is replaced with a measured value. Therefore, even if the second target voltage is initially set to a relatively large value, the second target voltage is reduced to approach the upper limit value of the variation of the first target voltage. As a result, variations in the output voltage VL of the DC voltage supply system 130 caused by the second power supply 132 operating in the constant voltage mode can be reduced.

(second modification)

As a second modification, a configuration for suppressing a change (increase) in the output voltage VL of the DC voltage supply system during the period from t5 to t6 in fig. 6, which is different from the first modification, will be described. In this modification, the current limit value is repeatedly changed in accordance with the current value IL supplied from the DC voltage supply system to the load.

Referring to fig. 11, the DC voltage supply system 140 according to the second modification is configured such that an ammeter 142 for measuring an output current value IL of the DC voltage supply system 140 and a current value transmission line 144 are added to the DC voltage supply system 100 shown in fig. 1. The ammeter 142 is, for example, a current sensor. The measured current value is transmitted to the control unit 108 via the current value transmission line 144. If the output signal (measurement value) from the ammeter 142 transmitted through the current value transmission line 144 is a digital signal (digital data), the control unit 108 receives the digital data as it is and stores the digital signal in, for example, the memory 122. If the output signal from the ammeter 142 transmitted through the current value transmission line 144 is an analog signal, the control unit 108 may be provided with an a/D converter to sample the signal and convert the signal into digital data.

Referring to fig. 12 and 13, a voltage supply operation of the DC voltage supply system 140 will be described. Fig. 12 is a flowchart of a change to return to step 300 if the result of the determination of step 306 in the flowchart of fig. 4 is otherwise. Fig. 13 is a flowchart of a change to return to step 406 if the result of the determination of step 408 in the flowchart of fig. 5 is otherwise.

The processing shown in fig. 12 is realized by the CPU 120 reading a predetermined program from the memory 122 and executing the program. As described above, after performing steps 300 to 304 and starting the voltage supply from the DC voltage supply system 140, the CPU 120 determines whether an instruction to stop the DC voltage supply system 140 is received in step 306. If it is determined that a stop instruction is received, control proceeds to step 308. Otherwise, control returns to step 300.

Therefore, until the stop instruction is received, steps 300 to 304 are repeated to cause the CPU 120 to repeatedly transmit the load current value to the second power supply 106. At this time, unlike the DC voltage supply system 100 in fig. 1, the load current value repeatedly transmitted by the second and subsequent processes in step 302 is a measured value of the current value IL measured by the ammeter 142. Note that step 304 is a process of transmitting a start instruction and thus repeatedly transmits a start instruction, but the first power supply 104 and the second power supply 106 may ignore the repeatedly transmitted start instruction.

The processing shown in fig. 13 is realized by the power supply internal control unit 152 reading a predetermined program from the internal memory and executing the program. As described above, through steps 400 to 404 and step 406, which is initially performed, if the output current value IL of the DC voltage supply system 140 is greater than the current limit value, the second power supply 106 operates in the constant current mode to output a current equal to the set current limit value, and a residual current of the current value IL of the current flowing to the load 110 is supplied from the first power supply 104. Thereafter, in step 408, the power supply internal control unit 152 determines whether a stop instruction is received from the control unit 108. If it is determined that a stop instruction is received, control proceeds to step 410. Otherwise, control returns to step 406. Thus, the processing in step 406 is repeated for the second time and thereafter until it is determined that the stop processing is performed.

In the repetition step 406, the power supply internal control unit 152 determines a current limit value from the load current value according to the load ratio a (0. ltoreq. a.ltoreq.1) of the second power supply 106 and sets the current limit value of the DC-DC unit 150 each time the load current value (the current value IL of the current flowing to the load 110) sent from the control unit 108 is acquired. Specifically, the power supply internal control unit 152 determines a value that is a multiple of the acquired load current value (measured value of the current value IL) as a new current limit value. Therefore, the output current of the second power supply 106 in the constant current mode is limited by the newly set current limit. In this modification, the power supply internal control unit 152 acquires the load current value from the control unit 108. However, the power supply internal control unit 152 may directly acquire the load current value from the ammeter 142. Alternatively, an ammeter for measuring the current output from the first power supply 104 instead of the load current value may be provided, and the power supply internal control unit 152 may receive the output of the ammeter and calculate the load current value based on the sum of the output of the ammeter and the current output from the second power supply 106

Referring to fig. 14, variations of voltage and current in the DC voltage supply system 140 will be described. In fig. 14, the uppermost graph shows the current value IL of the current supplied from the DC voltage supply system 140 and flowing to the load 110, as shown in fig. 6 and 10. The graphs for the second and third stages show the output currents (I1 and I2) of the first and

second power sources

104 and 106, respectively. The graph at the lowest level shows the output voltage VL of the DC voltage supply system 140.

The operations from starting the DC voltage supply system 140 and starting the voltage supply until time t2 (steps 400 to 404, and step 406 performed initially) are the same as in fig. 5. During this period, the current and voltage change in the same manner as in fig. 6. After time t2, in the DC voltage supply system 140, the process in step 406 is repeated for the second time and thereafter. That is, the process of setting a value that is a multiple (0. ltoreq. a.ltoreq.1) of the measurement value of the current value IL measured by the ammeter 142 as a new current limit value is repeatedly performed. Therefore, if the current value IL of the current flowing to the load 110 changes, the current limit value of the second power supply 106 also changes accordingly. Here, assume that a is 0.2.

In fig. 14, during a period from t2 to t8, the current value IL of the current flowing to the load 110 is constant (100A) and does not change. The measured value of the output current value I2 of the second power supply 106 is also constant (20A) and does not change. The current limit of the second power supply 106 is updated to the same value (20A).

During the period from t8 to t9, the current value IL of the current flowing to the load 110 decreases. During this time period, the current limit of the second power supply 106 will become 0.2 times the measured value each time the current value IL is measured. Therefore, the output current value I2 of the second power supply 106 in the constant current mode is a value 0.2 times (20%) the measured value of the current value IL measured last time. A residual current of 80% of the current value IL is supplied from the first power source 104. That is, during the period in which the current value IL of the current flowing to the load 110 changes, the output currents of the first power supply 104 and the second power supply 106 each change in proportion to the current value IL. The first power supply 104 operates in the constant voltage mode to supply current even if the current value IL has become less than an initial value (e.g., 20A) of the current limit. Therefore, the output voltage of the DC voltage supply system 140 is maintained in a state determined by the output voltage V1 of the first power supply 104. When the output current value I1 of the first power supply 104 changes, the output voltage VL of the DC voltage supply system 140 changes due to the voltage drop caused by the parasitic resistance 112, but the amount of change thereof is smaller than the amount of change Δ V2 shown in fig. 10.

In fig. 14, after time t9, the current value IL becomes constant and is a value (10A) smaller than the initial value of the current limit value. The current limit is repeatedly set to 2A (═ 0.2 × 10A). A current of 2A is supplied from the second power supply 106 (constant current mode), and a remaining current of 8A is supplied from the first power supply 104 (constant voltage mode).

Although not shown in fig. 14, also in the case where the current value IL is increased from 10A, the current limit value is also changed in the same manner. As a result, current is supplied from both the second power supply 106 (constant current mode) and the first power supply 104 (constant voltage mode).

In the second modification, the case where the current flowing to the load 110 is directly measured has been described. However, another method may be adopted as long as the output current value IL of the DC voltage supply system 140 can be found. For example, the output current value I1 of the first power supply 104 and the output current value I2 of the second power supply 106 may be measured, and the measured values may be added to calculate the output current value IL. The measurement values of the ammeters measuring the respective currents are transmitted to the control unit 108 in the same manner as described above. By adding the two measured values acquired by the control unit 108, the output current value IL of the DC voltage supply system 140 can be calculated.

In the second modification, even if the current value IL of the load 110 decreases, the current is supplied from the second power supply 106 unless the current value IL becomes 0. However, when the current value IL of the load 110 becomes smaller than a predetermined value, the current limit value may be set to 0 so that no current is output from the second power supply 106. In this case, current is supplied to the load 110 only from the first power source 104. At this time, the current supplied from the second power supply 106 becomes 0. To compensate for this, the output current value I1 of the first power supply 104 slightly increases, and therefore the voltage drop due to the parasitic resistance 112 slightly increases. Therefore, the output voltage VL of the DC voltage supply system 140 is slightly decreased, but the variation is not large.

For example, when the first power supply: second power supply ═ 4: 1, if the current value of the load is 100A, the current distribution is 80A: 20A. As described above, even if the current value of the load sharply decreases until the current value of the load decreases to 20A (sharp decrease 80A), the second power supply can be maintained in the constant current mode (the output voltage of the second power supply does not affect the output voltage of the DC voltage supply system). On the other hand, if the current of the load becomes 10A, the current distribution is 8A: 2A and if the change at this time is sharply reduced to only 2A, i.e., 8A, the second power supply enters the constant voltage mode. As described above, in the low load state where the current value of the load is relatively small, if the current value is set to 4: the ratio of 1 distributes the current, and the second power supply enters a constant voltage mode even if the load variation is small, thereby outputting the output voltage of the second power supply as the output voltage of the DC voltage supply system. To avoid this, it is preferable to set the current limit to 0A.

In the above description, the case where two power supplies are connected in parallel has been described. However, three or more power sources may be connected in parallel. In this case, one power source (corresponding to the first power source 104) is constantly operated by CV control. The other power supplies operate through CVCC control. The target voltage and current limits may be set as shown in the flow charts in fig. 3, 6, or 9. Therefore, a load concentration state in which only a specific power source supplies current to a load can be avoided. Current may be supplied to a load from multiple power sources at a desired load ratio.

In the above description, the case where the control unit 108 transmits the first target voltage and load current value to the second power supply and the second power supply determines the second target voltage and current limit values and sets them for the DC-DC unit 150 has been described. However, the present disclosure is not limited thereto. The functionality of the second power supply 106 for determining the second target voltage and current limit as described in the first embodiment may be assigned to the control unit 108 or may be assigned to the first power supply 104. Similarly, the function of the second power supply for determining the second target voltage and current limit as described in the first or second variation may be assigned to the control unit 108, or may be assigned to the first power supply 104.

In the case where the control unit 108 repeats the process of transmitting the measured value of the output current value IL of the DC voltage supply system 140 measured by the ammeter 142 to the second power supply 106, it takes time for each process of obtaining the measured value from the measurement of the output current value IL to the control unit 108. In addition, in the case of repeating the process of transmitting the measured value of the output current value IL to the second power supply 106, it takes some time for the control unit 108 to calculate a new current limit value. Further, in the case of repeating the process of determining a new current limit from the measured value of the output current value IL and transmitting the new current limit to the second power supply 106, it takes time from the control unit 108 outputting the new current limit to the second power supply 106 receiving the new current limit. In this case, for example, it is assumed that the output current value IL changes (decreases) sharply in a time shorter than the delay time from the measurement of the output current value IL to the reception of the new current limit value by the second power supply 106. In this case, the load current becomes smaller than the current limit value, and thus the second power supply 106 starts to operate in the constant voltage mode (CV control). As a result, the output voltage VL of the DC voltage supply system 140 increases.

To inhibit this, for example, the second power supply 106 itself may detect that the second power supply 106 is not operating in the constant current mode (is operating in the constant voltage mode). When such detection is performed, the set current limit value is decreased. Therefore, the second power supply 106 can be kept operating in the constant current mode (CC control). Therefore, even in the case where the load current changes abruptly and there is some delay before the new current limit value is received from the control unit 108, an increase in the output voltage of the DC voltage supply system can be suppressed. Note that when it is detected that the second power supply 106 is not operating in the constant current mode, the second power supply 106 may set the current limit to 0.

For example, the second power supply 106 may be provided with a state detection unit for detecting an operation mode of the second power supply 106 itself, and may detect that the second power supply 106 is not operating in the constant current mode. When the state detection unit has detected that the second power supply 106 is not operating in the constant current mode, the second power supply 106 may immediately decrease the current limit value currently set.

In order to detect that the second power supply 106 is not operating in the constant current mode, measurement of the output current value I2 may be performed inside the second power supply 106 instead of providing a state detection unit. For example, inside the second power supply 106, the output terminal and the power supply internal control unit 152 may be connected to each other via a wire and an a/D converter. The power supply internal control unit 152 of the second power supply 106 may detect that the second power supply 106 is not operating in the constant current mode if the acquired current value (measured value) is less than the set current limit value. The power supply internal control unit 152 can immediately reduce the current limit to a value that is less than the measured value and not less than 0.

In order to detect that the second power supply 106 is not operating in the constant current mode, in the configuration shown in fig. 11, an ammeter for measuring the output current value I2 of the second power supply 106 may be provided outside the second power supply 106, and the measured value may be transmitted to the second power supply 106, or whether the output voltage of the second power supply 106 is equal to the second target voltage may be measured.

In the first embodiment, the first modification, and the second modification described above, there may be a case where the first power supply 104 is stopped for some reason (malfunction, etc.). In this case, the second power supply 106 will operate in a constant voltage mode (CV control) so that the output voltage VL of the DC voltage supply system increases. As a measure thereof, a determination unit for determining whether the first power supply 104 is stopped is preferably provided. The influence when operating in the constant voltage mode can be minimized by the determination unit detecting the stop of the first power supply 104 and changing the second target voltage and the current limit. In this way, even when the first power supply 104 is stopped due to a failure or the like, an increase in the output voltage of the DC voltage supply system can be suppressed.

For example, whether the first power supply 104 is stopped may be determined by the control unit 108 or the second power supply 106 monitoring a predetermined output signal from the first power supply 104. For example, through self-diagnosis, the first power supply 104 may output a signal of a first level (e.g., a high level) at the time of normal operation, and may output a signal of a second level (e.g., a low level) at the time of abnormal operation. By determining the level of the output signal, the control unit 108 or the second power supply 106 may determine whether the first power supply 104 is stopped. In the case where the second power supply 106 monitors the output signal from the first power supply 104, when the level of the output signal has changed to the second level, the currently set second target voltage and current limit may be changed to a new second target voltage and a new current limit. The new current limit is greater than the current limit currently set and is, for example, a rated maximum current value that is the maximum value of the current that the second power supply 106 can stably output. The new second target voltage is less than the currently set second target voltage. Since the value of the parasitic resistance 112 is not much different from the value of the parasitic resistance 114, it is preferable that the new second target voltage is equal to or close to the first target voltage.

In case the control unit 108 monitors the output signal from the first power supply 104, a new second target voltage and a new current limit may be sent from the control unit 108 to the second power supply 106 when the level of the output signal has changed to the second level.

In the above description, the case where the first power supply 104 and the second power supply 106 are DC-DC converters that convert the DC output voltage of the battery 102 has been described. However, the present disclosure is not limited to this configuration. The first power supply 104 may be a power supply that operates in a constant voltage mode by CV control, the second power supply may be a power supply that can operate in a constant voltage mode and a constant current mode by CVCC control, and the DC voltage supply system may be constituted by a plurality of such power supplies. Note that, as described above, three or more power supplies may be connected in parallel, and in the case where three or more power supplies are connected in parallel, one power supply may be operated by CV control, and the other power supplies may be operated by CVCC control.

(second embodiment)

[ INTEGRAL CONFIGURATION ]

The first embodiment relates to a DC-DC converter. However, the present disclosure is not limited to such embodiments. The present disclosure is also applicable to a DC-AC converter, an AC-AC converter, or an AC-DC converter. An AC voltage supply system according to a second embodiment described below includes an inverter that performs DC-AC conversion.

Fig. 15 shows a schematic configuration of an AC voltage supply system 500 according to the second embodiment. Referring to fig. 15, an AC voltage supply system 500 is supplied with a DC voltage from a battery 502, and the AC voltage supply system 500 supplies a load 504 with an AC voltage.

The AC voltage supply system 500 includes a first power source 520 and a second power source 522 connected in parallel between the high voltage battery 502 and the load 504. The AC voltage supply system 500 is used for, for example, an electric vehicle or the like, and supplies an AC voltage to a load 504 such as a household appliance at a constant voltage.

Although shown with a single line in fig. 15, the DC voltage from the battery 502 is supplied to each of the first power supply 520 and the second power supply 522 through a pair of two lines (i.e., a connection line connected to the positive electrode of the battery 502 and a connection line connected to the negative electrode of the battery 502). The output of the first power supply 520 and the output of the second power supply 522 are connected to the connection node and then to the load 504 via the connection line 506. The AC voltage supply system 500 further includes a parasitic resistance 526 that exists between the first power supply 520 and the connection node, a parasitic resistance 528 that exists between the second power supply 522 and the connection node, and a bus 524 that allows communication between the first power supply 520 and the second power supply 522.

Also in the following description, as in the first embodiment, the output voltage and the output current value of the first power supply 520 are defined as the output voltage V1 and the output current value I1, and the output voltage and the output current value of the second power supply 522 are defined as the output voltage V2 and the output current value I2. The voltage and current values supplied to the load 504 via the connection line 506 are defined as a voltage VL and a current value IL. The parasitic resistance 526 and the parasitic resistance 528 are substantial resistances on the traces, including the resistance of the wires, the resistance of the connection portion, and the like, and have resistance values R1 and R2, respectively.

Fig. 16 shows a configuration of the first power supply 520. Referring to fig. 16, the first power supply 520 includes: an inverter unit 550 receiving the DC voltage from the battery 502, converting the DC voltage into an AC voltage having a rectangular waveform, and outputting the AC voltage; a power supply internal control unit 552 that includes a microprocessor and adjusts the duty ratio and ON/OFF timing of the semiconductor switching elements in the inverter unit 550 so that the AC voltage to be supplied to the load 504 becomes a target value (first target voltage), thereby performing constant voltage control ON the first power supply 520; a current sensor 554 formed of a Current Transformer (CT), and measuring a current output from the inverter unit 550 and outputting an analog measurement signal; an a/D conversion circuit 556 that a/D converts an analog signal from the current sensor 554 and inputs the resultant signal to the power supply internal control unit 552; and a target voltage storage unit 558 that stores a target voltage for constant voltage control of the first power supply 520 by the power supply internal control unit 552 and supplies the target voltage to the power supply internal control unit 552.

The power supply internal control unit 552 may communicate with the second power supply 522 via the bus 524, and in the present embodiment, sends a current value I1 detected by the current sensor 554.

In the present embodiment, the inverter unit 550 is a full-bridge type inverter, and includes switching elements Q1, Q2, Q3, Q4 connected in a full-bridge form. The drain of the switching element Q1 is connected to the positive electrode of the battery 502. The source of switching element Q1 is connected to the drain of switching element Q2 at node 562. The source of the switching element Q2 is connected to the negative electrode of the battery 502. The drain of the switching element Q3 is connected to the positive electrode of the battery 502. The source of switching element Q3 is connected to the drain of switching element Q4 at node 564. The source of the switching element Q4 is connected to the negative electrode of the battery 502.

In order to convert the output voltage into a different voltage, for example, a DC-DC unit may be provided at a stage before the inverter unit 550, or a voltage conversion unit using a transformer may be provided at a stage after the inverter unit 550.

Node 562 and node 564 are connected to the positive and negative power supply terminals, respectively, of the load 504. In this embodiment, a current sensor 554 is provided to measure the current on the connection line from node 562 to load 504.

Fig. 17 shows a configuration of the second power supply 522. Referring to fig. 17, the second power supply 522 includes: an inverter unit 580 having the same configuration as the inverter unit 550 in fig. 16; a current sensor 585 for measuring an output current value I2 of the inverter unit 580; a voltage sensor 587 for measuring an output voltage V2 of the inverter unit 580; a power supply internal control unit 582 for controlling so that the current value from the inverter unit 580 becomes a target value; an a/D conversion circuit 588 that a/D converts an analog signal indicating a current value I2 output from the current sensor 585 and inputs the resultant signal to the power supply internal control unit 582; and an a/D conversion circuit 589 that a/D converts the analog signal indicating the output voltage V2 output from the voltage sensor 587 and inputs the resultant signal to the power supply internal control unit 582.

The second power supply 522 further includes: a timer 584 for measuring the elapse of a predetermined period of time from the start of the second power supply 522(AC voltage supply system 500); and an operation prohibition signal generation circuit 586 that outputs a signal for prohibiting the power conversion operation of the inverter unit 580 to the power supply internal control unit 582 based on the output of the timer 584 until a predetermined period of time elapses from the start-up. When the timer 584 detects that the predetermined period of time has elapsed, the operation prohibition signal is canceled (disabled), and the inverter unit 580 is started. In the present embodiment, when the operation prohibition signal is at a high level, the power conversion operation of the inverter unit 580 is prohibited, and when the operation prohibition signal is at a low level, the power conversion operation is permitted. The combination may be reversed, or the prohibition/cancellation may be specified by a digital signal of two or more bits. With this configuration, the inverter unit 580 is started with a delay of a predetermined period of time after the second power supply 522 is started (i.e., after the first power supply 520 is started).

The second power supply 522 further includes an initial target voltage storage unit 590 storing an initial target voltage value of the second power supply 522; a rewritable target voltage storage unit 592 storing a target voltage value for the second power supply 522 to perform a constant voltage operation; an initial current limit storage unit 594 that stores an initial current limit of the second power supply 522 and inputs the initial current limit to the power supply internal control unit 582; and a rewritable current limit storage unit 596 storing a current limit value to be updated with the operation of the second power supply 522. The initial target voltage value of the second power supply 522 is greater than the target voltage value of the first power supply 520. Therefore, after the predetermined period of time has elapsed from the start-up of the first power supply 520, the second power supply 522 can be started up without any problem.

Fig. 18 is a flowchart showing a control structure of a computer program for operating the power supply internal control unit 582 in the AC voltage supply system 500 according to the present embodiment to realize the function of the second power supply 522. Referring to fig. 18, the program includes: step 600, after starting the AC voltage supply system 500, waiting during a period in which the operation inhibition signal input from the operation inhibition signal generation circuit 586 is at a high level, so that the second power supply 522 is started later than the first power supply 520; step 602, when the operation prohibition signal changes to the low level, reads the initial value of the target voltage (second target voltage) at which the second power supply 522 performs the constant voltage operation from the initial target voltage storage unit 590 and writes the initial value into the target voltage storage unit 592; and a step 604 of reading an initial value of the limit value of the current output from the second power supply 522 from the initial current limit storage unit 594 and writing the initial value into the current limit storage unit 596.

The above procedure further comprises, after step 604: step 606, performing both constant voltage control using the second target voltage and constant current control using the current limit, and calculating control variables of both controls; step 608 of performing output arbitration to select a control variable whose current value becomes smaller from the control variables output in step 606; a step 610 of outputting an operation (duty ratio) of the switching element of the inverter unit 580 according to the control variable selected by the arbitration in the step 608; step 612, determining whether an instruction to stop operation is received, and branching a control flow according to the determination result; and step 618 of executing the stop processing in response to the determination in step 612 that the stop command is received, and ending the execution of the program.

The above program further includes: step 613, when the determination in step 612 is negative, measuring the output voltage V2 of the second power supply 522; step 614, resetting (updating) the second target voltage to the current output voltage V2 of the second power supply 522; at step 615 following step 614, measuring the output current value I2 of the second power supply 522 and reading the output current value I1 of the first power supply 520 sent from the first power supply 520; step 616, calculating the current limit I of the second power supply 522 according to the following expression (1)_TS(ii) a And a step 617 of updating the current limit value of second power supply 522 stored in target voltage storage unit 592 (fig. 17) by the value calculated in step 616, and returning the control to step 606. In the present embodiment, the power supply internal control unit 582 receives the output current value I1 of the first power supply 520 from the first power supply 520. However, the power supply internal control unit 582 may directly receive the output of the current sensor 554.

[ mathematical formula 1]

Note that I_TSIs the current limit of the second power supply 522, I1 is the value of the load current output from the first power supply 520, I2 is the value of the load current output from the second power supply 522 Rated_MIs a rating of the first power supply 520, and Rated_SIs the rating of the second power supply 522. Here, the current value is an effective value of the current output from the inverter unit. The voltage value is an effective value of the voltage output from the inverter unit. Since the current limit value is thus updated in

steps

616 and 617, the output current value I2 of the second power supply 522 always becomes smaller than the load current value IL. Therefore, in the present embodiment, the second power supply 522 does not operate in the constant voltage mode. In expression (1), the sum (I1+ I2) of I1 and I2 represents the value of the load current output from the AC voltage supply system 500. The value multiplied by the sum is a value not less than 0 and less than 1. This value is a target value determined by the nominal values of the first power supply 520 and the second power supply 522. The expression (1) can also be interpreted such that the current limit I is_TSThe ratio to the current value (I1+ I2) supplied from the voltage supply system 500 is equal to a value not less than 0 and less than 1.

In addition, as described in the first modification of the first embodiment, by resetting the second target voltage to the present output voltage of the second power supply 522 in step 614, the second target voltage of the second power supply 522 becomes an initial value smaller than the second target voltage.

In the present embodiment, I1 represents the value of the load current output from the first power supply 520. However, the present disclosure is not limited to such embodiments. As I1, any value may be used as long as the value is used as a reference for estimating or calculating the value of the load current to be output from the second power supply 522. For example, IL output from the AC voltage supply system 500 may be used as I1. In this case, a voltage sensor may be provided to the connection line 506 shown in fig. 15.

Operation of AC Voltage supply System

The AC voltage supply system 500 described above operates as follows. When the operation of the AC voltage supply system 500 is started, the operation of the second power supply 522 is prohibited. Only the first power supply 520 operates and the second power supply 522 does not operate. The first power supply 520 initially reads a first target voltage from the target voltage storage unit 558 and then operates by constant voltage control in the same manner as the first power supply 104 except that the output is AC instead of DC. At this time, the power supply internal control unit 552 of the first power supply 520 receives the load current value measured by the current sensor 554 from the a/D conversion circuit 556, and transmits the load current value to the second power supply 522 via the bus 524 at regular intervals.

Until a predetermined period of time elapses from the start-up of the second power supply 522, the operation inhibition signal generation circuit 586 supplies an operation inhibition signal to the power supply internal control unit 582. The power supply internal control unit 582 does not drive the inverter unit 580, and no current is output from the second power supply 522.

When the predetermined period of time has elapsed, the timer 584 detects the elapse, and sends a timer expiration signal to the operation inhibition signal generation circuit 586. In response to the timer expiration signal, the operation inhibition signal generation circuit 586 stops outputting the operation inhibition signal. As a result, the current output from the second power supply 522 is started under the control of the power supply internal control unit 582 (step 602 and subsequent steps in fig. 18). Since the second target voltage for the second power supply 522 is set to be greater than the first target voltage for the first power supply 520, the second power supply 522 may start current output.

The power supply internal control unit 582 of the second power supply 522 sets the initial value of the second target voltage (step 602). Specifically, the power supply internal control unit 582 reads an initial target voltage from the initial target voltage storage unit 590, and stores the initial target voltage in the target voltage storage unit 592. The initial value has been stored in the initial target voltage storage unit 590 in fig. 17. The initial value is set to be slightly larger than the first target voltage for constant voltage control of the first power supply 520. For example, if the first target voltage is 15V, the second target voltage is set to about 18V. The second target voltage is updated along with the operation of the second power supply 522, as described later.

The power supply internal control unit 582 also sets an initial value of the current limit (step 604).Specifically, power supply internal control unit 582 reads the initial value of the current limit from initial current limit storage unit 594 and stores the initial value in current limit storage unit 596. The current limit is also updated as described later. Subsequently, the power supply internal control unit 582 is based on the preset rating Rated of the first power supply 520 and the second power supply 522_MAnd Rated_S(output current), the output current value I1 of the first power supply 520 sent from the power supply internal control unit 552 of the first power supply 520, and the output current value I2 of itself, the current limit value ITS of the second power supply 522 is determined using the above expression (1) (step 606). Thereafter, arbitration is performed between the controlled variable of the constant voltage control and the controlled variable of the constant current control performed with the second target voltage, based on the current limit value ITS determined by the above expression (1) (step 608). Here, a control variable of the constant current control is selected. Then, the selected control variable is output, and the inverter unit 580 is driven by a control signal according to the control variable.

Further, the second target voltage is replaced with the current output voltage of the second power supply 522 (step 614). The output voltage VL of the AC voltage supply system 500 is determined by the output voltage V1 of the first power supply 520 operating in a constant voltage mode. The output voltage VL of the AC voltage supply system 500 becomes a value obtained by subtracting a voltage drop due to the parasitic resistance 528 from the output voltage V2 of the second power supply 522. Therefore, as described above, by updating the second target voltage, the second target voltage becomes smaller than its initial value.

Thereafter, the current limit of the second power supply 522 is updated according to expression (1). By this update, the current limit value of the second power supply 522 always becomes smaller than the load current value IL. The output current of the second power supply 522 is never equal to or greater than the load current value IL, and the second power supply 522 operates substantially only in the constant current mode. That is, in a state where the output voltage of the second power supply 522 approaches to reach the second target voltage, the first power supply 520 does not output a current, and only the second power supply 522 outputs a current. In this state, there is a possibility that a voltage variation described as a problem of the conventional technique is caused. However, in the present embodiment, since the current limit value of the second power supply 522 is updated according to expression (1), both the first power supply 520 and the second power supply 522 always carry the load current at a certain rate, and thus the above-described problem does not occur.

If a stop instruction is received (yes in step 612), control proceeds to step 618 to execute stop processing, thereby ending execution of the program.

As described above, according to the present embodiment, in the AC voltage supply system 500, both the first power supply 520 and the second power supply 522 can be operated, and the load concentration in which the current is supplied to the load 504 from only one power supply can be prevented. The current supply to the load 504 can be distributed between the two power sources, whereby a state in which only a specific power source operates for a long time and the lives of the plurality of power sources become unequal can be prevented.

In this embodiment, when the second power supply 522 begins to operate, the first power supply 520 and the second power supply 522 each carry a portion of the load current and both operate. When the load current changes, switching does not occur between a load current region in which only the first power supply 520 operates and a load current region in which the first power supply 520 and the second power supply 522 operate. As a result, the occurrence of voltage variation due to such switching can be prevented.

(variants)

In the above embodiment, I1 represents the value of the load current output from the first power supply 520. However, the present disclosure is not limited to such embodiments. As I1, any value may be used as long as the value is used as a reference for estimating or calculating the value of the load current output from the second power supply 522. For example, IL output from the AC voltage supply system 500 may be used as I1. In this case, a voltage sensor may be provided to the connection line 506 shown in fig. 15.

Alternatively, I1 may be a value representing the current on the input side of the first power supply 520. In this case, as shown in fig. 19, a current sensor 650 may be provided on the input side of the first power supply 630.

The first power supply 630 shown in fig. 19 differs from the first power supply 520 in that the first power supply 630 includes an inverter unit 640 having a current sensor 650 on the input side, instead of the inverter unit 550 shown in fig. 16, and the first power supply 630 includes an a/D conversion circuit 652 that a/D converts an analog signal output from the current sensor 650 and supplies the resultant signal to a power supply internal control unit 552, instead of the a/D conversion circuit 556 shown in fig. 16. In this case, it cannot be said that the current value measured by the current sensor 650 is the output current value of the first power source 630. However, the output current of the first power supply 630 may be estimated based on the output of the current sensor 650. For example, the output current of the first power source 630 may be estimated by the following expression.

[ mathematical formula 2]

Note that I_TSIs the current limit of the second power supply 522, I1 is a reference value and is the output of the current sensor 650 on the input side of the inverter unit 640 received from the first power supply 520, C1 is a coefficient for estimating the output current of the first power supply 520 from I1, I2 is the output of the current sensor shown in fig. 17, Rated_MIs a rating of the first power supply 520, and Rated_SIs the rating of the second power supply 522.

A process of estimating the output current value of the first power supply 520 by multiplying the current value I1 as the reference value by the coefficient C1 may be performed in the power supply internal control unit 552. Unlike the configuration shown in fig. 19, for example, in the case where a DC-DC unit for voltage conversion is provided at a stage before the inverter unit 640, or in the case where a transformer for voltage conversion is provided at a stage after the inverter unit 640, the output current of the first power source 630 can be estimated from the current measured at any portion in such a configuration using, for example, the step-down ratio of the transformer. The estimated output current of the first power supply 630 may be sent from the power supply internal control unit 552 to the second power supply 522.

The value sent from the first power source 630 to the second power source 522 may not be the output current of the first power source 630. A value including information equivalent to the output current of the first power source 630 may be used. For example, the load ratio (output current value/rated value) of the first power source 630 may be used, or information other than that may be used. In the case of the sensor arrangement as shown in fig. 19, instead of the output current of the first power supply 630 estimated by the power supply internal control unit 552, the current value measured by the current sensor 650 may be transmitted to the second power supply 522. In this case, the output current of the first power supply 630 can be estimated on the second power supply 522 side. The analog signal output from the current sensor 650 may also be directly transmitted to the second power supply 522 if the situation permits, and the analog signal is converted into a digital signal and processed on the second power supply 522 side.

(third embodiment)

Fig. 20 is a block diagram showing the configuration of an AC voltage supply system according to the third embodiment. Referring to fig. 20, an AC voltage supply system 770 according to the present embodiment has a configuration similar to the AC voltage supply system 500 shown in fig. 15, but is different from the AC voltage supply system 500 in that the AC voltage supply system 770 further includes a voltage sensor 780, the voltage sensor 780 measuring an output voltage of the first power supply 520 in fig. 15 and outputting an analog signal, and instead of the second power supply 522 in fig. 15, the AC voltage supply system 770 includes a second power supply 782 receiving an output of the voltage sensor 780, the second power supply 782 being switchably operable between a constant voltage mode using a target voltage higher than a target voltage of the first power supply 520 and a constant current mode based on a current limit, like the second power supply 522

Referring to fig. 21, the second power supply 782 is different from the second power supply 522 shown in fig. 17 as follows. The voltage sensor 587 is removed from the second power supply 522 shown in fig. 17, and instead of the voltage sensor 587, an a/D conversion circuit 589 receives the output of the voltage sensor 780 shown in fig. 20, performs a/D conversion, and outputs a digital signal. The second power supply 782 does not include the timer 584 and the operation prohibition signal generation circuit 586 shown in fig. 20. Instead of the power supply internal control unit 582 shown in fig. 20, the second power supply 782 includes a power supply internal control unit 790, and after starting the AC voltage supply system 770, the power supply internal control unit 790 stops the inverter unit 580 until the output voltage of the first power supply 520 received from the voltage sensor 780 becomes equal to the first target voltage, and starts the power conversion operation of the inverter unit 580 in response to the fact that the output voltage of the first power supply 520 has become equal to the first target voltage. Except for the above, the second power supply 782 has the same configuration as the second power supply 522.

In the third embodiment, after starting the AC voltage supply system 770, the power supply internal control unit 790 stops the driving signal to the inverter unit 580. That is, although the power supply internal control unit 790 calculates the value of the driving signal for the inverter unit 580 required for outputting the current in the constant current mode, the power supply internal control unit 790 opens the contact of the output switch for the driving signal with the inverter unit 580, thereby not outputting the driving signal. As a result, immediately after the AC voltage supply system 770 is started, the inverter unit 580 does not operate, and does not perform the current output from the second power supply 782. The power supply internal control unit 790 monitors the output voltage V1 of the first power supply 520 supplied from the voltage sensor 780 via the a/D conversion circuit 589 in this state. If the output voltage V1 of the first power supply 520 has become equal to the first target voltage, this means that power conversion in the first power supply 520 is started. In this case, the power supply internal control unit 790 starts outputting the driving signal to the inverter unit 580. Since the target voltage of the second power supply 782 is greater than the first target voltage in the constant voltage mode, the second power supply 782 may output a current. On the other hand, the current limit of the second power supply 782 is determined such that the ratio of the current limit to the sum of the output current of the first power supply 520 and the output current of the second power supply 782 satisfies expression (1), as in each of the embodiments described above. With this value, the second power supply 782 operates in a constant current mode, and the current for the load is divided between the first power supply 520 and the second power supply 782. The second power supply 782 does not operate in the constant voltage mode, and a voltage change due to a change in the operation mode from the constant voltage mode of the first power supply 520 to the constant voltage mode of the second power supply 782 can be prevented. As a result, it is possible to provide a voltage supply system and a power supply that enable the power supply to be set to a desired load ratio. In addition, it is possible to suppress variation in the output voltage of the voltage supply system due to variation in the load current. In the present embodiment, the start of power conversion in the first power supply 520 is detected from the fact that the output voltage V1 of the first power supply 520 has become equal to the first target voltage. However, the present disclosure is not limited to such embodiments. The first power supply 520 itself may determine that the first power supply 520 has initiated power conversion, and may send a signal indicative of this action to the power supply internal control unit 790.

(fourth embodiment)

The fourth embodiment relates to an AC voltage supply system that includes a first power source and a second power source, and converts a DC voltage from a battery into a predetermined AC voltage and outputs the AC voltage, as in the third embodiment.

Fig. 22 is a block diagram showing the configuration of the first power supply 800 in the fourth embodiment. Referring to fig. 22, the first power supply 800 has a configuration similar to that of the first power supply 520 shown in fig. 16. The difference is that the first power supply 800 further includes a voltage sensor 810 for measuring the output voltage of the inverter unit 550, and an a/D conversion circuit 812 for converting an analog voltage signal output from the voltage sensor 810 into a digital signal, and instead of the power supply internal control unit 552 in fig. 16, the first power supply 800 includes a power supply internal control unit 814 further having a function of outputting a signal indicating the output voltage of the inverter unit 550 supplied from the a/D conversion circuit 812 to the bus 524.

Fig. 23 is a block diagram showing the configuration of the second power supply 830 in the fourth embodiment. Referring to fig. 23, the second power supply 830 differs from the power supply internal control unit 582 (see fig. 17) of the third embodiment in that the second power supply 830 does not include the a/D conversion circuit 589, the timer 584, and the operation prohibition signal generation circuit 586 shown in fig. 17, and in that, instead of the power supply internal control unit 582 in fig. 17, the second power supply 830 includes a power supply internal control unit 832 that, after the AC voltage supply system including the first power supply 800 and the second power supply 830 is started, stops the inverter unit 580 until the output voltage of the first power supply 800 received from the first power supply 800 via the bus 524 becomes equal to the first target voltage, and starts the power conversion operation of the inverter unit 580 in response to the fact that the output voltage of the first power supply 800 has become equal to the first target voltage.

The operation of the AC voltage supply system according to the present embodiment is the same as that in the third embodiment. After the AC voltage supply system according to the present embodiment is started, the power supply internal control unit 832 stops the driving signal to the inverter unit 580. That is, although the power supply internal control unit 832 calculates a value of a driving signal for the inverter unit 580 required for outputting a current in the constant current mode, the power supply internal control unit 832 disconnects the output switch for the driving signal from the inverter unit 580, thereby not outputting the driving signal. As a result, immediately after the AC voltage supply system is started, the inverter unit 580 does not operate, and current output from the second power source 830 is not performed. The power supply internal control unit 832 monitors the output voltage V1 of the first power supply 800 supplied from the first power supply 800 via the bus 524 in this state. If the output voltage V1 of the first power supply 800 has become equal to the first target voltage, this means that power conversion in the first power supply 800 is started. In this case, the power supply internal control unit 832 starts to output the driving signal to the inverter unit 580. Since the target voltage of the second power supply 830 is greater than the first target voltage in the constant voltage mode, the second power supply 830 may output a current. On the other hand, the current limit of the second power supply 830 is determined such that the ratio of the current limit to the sum of the output current of the first power supply 800 and the output current of the second power supply 830 satisfies expression (1). With this value, the second power supply 830 operates in a constant current mode, and the current for the load is divided between the first power supply 800 and the second power supply 830. The second power supply 830 does not operate in the constant voltage mode, and the operation mode does not change from the constant voltage mode of the first power supply 800 to the constant voltage mode of the second power supply 830. Therefore, a voltage change due to a change in the operation mode can be prevented. As a result, it is possible to provide a voltage supply system and a power supply that enable the power supply to be set to a desired load ratio. In addition, it is possible to suppress variation in the output voltage of the voltage supply system due to variation in the load current. Also in the present embodiment, the start of power conversion in the first power supply 800 may be detected by the power supply internal control unit 832 receiving a signal indicating that the first power supply 800 is started from the first power supply 800.

The above description includes features in the following additional notes.

(additional note 1) a DC power supply for use in a DC voltage supply system, comprising a constant voltage power supply configured to output a DC voltage in a constant voltage mode based on a first target voltage, the DC power supply being connected in parallel with the constant voltage power supply, the DC power supply comprising

A voltage generating unit configured to switchably output a voltage between a constant voltage mode based on a second target voltage greater than the first target voltage and a constant current mode based on a current limit.

(additional Note 2) the DC power supply according to additional Note 1, wherein

During a predetermined period of time after the DC voltage supply system is started, the current limit is set to 0, and

after a predetermined period of time has elapsed, the current limit is set to a predetermined value greater than 0.

(additional Note 3) the DC power supply according to additional Note 1, wherein

The current limit value is a value obtained by multiplying a current value of the current supplied from the DC voltage supply system by a value not less than 0 and not more than 1.

(additional note 4) the DC power supply according to any one of additional notes 1 to 3, wherein

The second target voltage is a value greater than an upper limit of variation of the DC voltage output from the constant voltage power supply based on the first target voltage.

(additional note 5) the DC power supply according to any one of additional notes 1 to 3, wherein

The second target voltage is a value equal to an upper limit of variation of the DC voltage output from the constant voltage power supply based on the first target voltage.

(additional note 6) the DC power supply according to any one of additional notes 1 to 5, wherein,

after the DC voltage supply system is started up, if the voltage generating unit has started to output the voltage in the constant current mode, the second target voltage is replaced with the voltage output from the DC power supply.

(additional note 7) the DC power supply according to any one of additional notes 1 to 6, further comprising: a state detection unit configured to detect an operation state of the DC power supply, wherein

The current limit value is reduced to a value not less than 0 in response to the fact that the state detection unit has detected that the DC power supply is not operating in the constant current mode.

(additional note 8) the DC power supply according to any one of additional notes 1 to 6, further comprising: a measurement unit configured to measure an output current of the DC power supply, wherein

The current limit value is reduced to a value not less than 0 in response to the fact that the output current measured by the measurement unit has become less than the current limit value.

(additional note 9) the DC power supply according to any one of additional notes 1 to 8, further comprising: a determination unit configured to determine whether the constant voltage power supply is stopped, wherein

In response to the fact that the determination unit has determined that the constant voltage power supply is stopped, the second target voltage is replaced with the first target voltage, and the current limit value is replaced with a rated maximum current value of the DC power supply.

(additional Note 10)

A DC voltage supply system comprising:

a first power supply configured to output a DC voltage in a constant voltage mode based on a first target voltage; and

a second power supply connected in parallel with the first power supply, wherein

The second power supply includes a voltage generating unit configured to switchably output a voltage between a constant voltage mode based on a second target voltage greater than the first target voltage and a constant current mode based on a current limit.

(additional Note 11)

A power supply control device for use in a voltage supply system including a constant voltage power supply configured to output a voltage in a constant voltage mode based on a first target voltage, the power supply control device being configured to control a power supply connected in parallel with the constant voltage power supply,

the power supply is a power conversion circuit configured to convert an input voltage into a predetermined output voltage and output the converted output voltage, the power conversion circuit including a plurality of switching elements connected to convert the input voltage into the output voltage and output the converted output voltage, the power supply control device including:

a current sensor configured to measure an output current of the power conversion circuit;

a voltage sensor configured to measure an output voltage of the power conversion circuit;

a timer configured to detect that a predetermined period of time has elapsed after the voltage supply system is started, and output a detection signal; and

a computer configured to receive outputs of the current sensor and the timer and having an output for driving the plurality of switching elements, wherein

The computer is programmed to

Maintaining the power conversion circuit in a stopped state when the voltage supply system is started,

determining an initial value of a current limit value for the power conversion circuit in response to a detection signal from the timer and starting the power conversion circuit, an

The following control procedures are repeatedly performed, and

in the control process, the computer is programmed to

The power conversion circuit is driven so as to obtain a current corresponding to the current limit at the output of the power conversion circuit, and

the current limit value is updated by applying a predetermined calculation expression to the output of the current sensor, the output current of the voltage supply system, or the output current of the constant-voltage power supply.

(additional Note 12)

The power supply control device according to additional note 11, wherein

The computer is connected to receive a reference value for calculating an output current of the constant voltage power supply from the constant voltage power supply, and

the computer is programmed to apply the calculation expression with respect to the output of the current sensor and the reference value when updating the current limit value in the control process, thereby updating the current limit value.

(additional Note 13)

The power supply control device according to additional note 12, wherein

The computational expression is the following expression:

[ mathematics 3]

Wherein, I_TSIs the current limit, I1 is the reference value, I2 is the output of the current sensor, Rated_MIs a rating of a constant voltage power supply, and Rated_SIs a rating of the power conversion circuit.

(additional Note 14)

The power supply control device according to additional note 12, wherein

The computational expression is the following expression:

[ mathematics 4]

Wherein, I_TSIs a current limit value, I1 is a reference value, C1 is a coefficient for estimating an output current of the constant voltage power supply from the reference value, I2 is an output of the current sensor, Rated_MIs a rating of a constant voltage power supply, and Rated_SIs a rating of the power conversion circuit.

(additional Note 15)

The power supply control device according to any one of additional notes 11 to 14, wherein

The computer includes a memory in which a plurality of memory cells are stored,

the computer is programmed to

In response to the fact that the power conversion circuit is started, an initial value of a second target voltage is stored in the memory, the second target voltage being a target value of an output voltage of the power conversion circuit, the second target voltage being greater than a first target voltage, the first target voltage being a target value of an output voltage of the constant voltage power supply, and

in the control process, the computer is further programmed to

Controlling the power conversion circuit so that an output voltage of the power conversion circuit does not exceed a second target voltage stored in the memory, and

the second target voltage stored in the memory is updated by the output value of the voltage sensor after the power conversion circuit is controlled.

Although the present disclosure has been described through the description of the above embodiments, the above embodiments are merely illustrative, and the present disclosure is not limited to the above embodiments only. With reference to the above description, the scope of the present invention is defined by each claim of the scope of the claims, and includes meanings equivalent to the wording described therein and all modifications within the scope of the claims.

List of reference numerals

100. 130, 140 DC voltage supply system

102. 502 battery

104. 520, 630, 800 first power supply

106. 132, 522, 782, 830 second power supply

108 control unit

110. 504 load

112. 114, 526, 528 parasitic resistance

116 connecting node

120 CPU

122 memory

124. 154 IF cell

126. 524 bus

134 voltmeter

142 ammeter

144 current value transmission line

150 DC-DC unit

152. 552, 582, 790, 814, 832 power supply internal control unit

200 rectangle

202. 204 circle

300. 302, 304, 306, 308, 400, 402, 404, 406, 408, 410, 420, 600, 602, 604, 606, 608, 610, 612, 613, 614, 615, 616, 617, 618 steps

500. 770 AC voltage supply system

506 connecting line

550. 580, 640 inverter unit

554. 585, 650 Current sensor

556. 588, 589, 652 and 812A/D conversion circuit

558. 592 target voltage memory cell

562. 564 node

584 timer

586 operation inhibiting signal generating circuit

587. 810 voltage sensor

590 initial target voltage memory cell

594 initial current limit memory cell

596 Current Limit memory cell

Coefficient of C1

Q1, Q2, Q3, Q4 switching elements

R1 and R2 resistance values

Output voltage of V1 first power supply

Output voltage of V2 second power supply

Output voltage of VL voltage supply system

I1 output Current of first Power supply

I2 output Current of second Power supply

Output current of IL voltage supply system

Claims

1. A power supply for use in a voltage supply system including a constant voltage power supply configured to output a voltage in a constant voltage mode based on a first target voltage, the power supply being connected in parallel with the constant voltage power supply, the power supply comprising:

2. The power supply of claim 1, further comprising: a delay unit configured to delay start of power conversion in the power supply until the constant voltage power supply starts power conversion.

3. The power supply of claim 2, wherein

The delay unit includes a delay start unit configured to start power conversion in the power supply with a delay of a predetermined period of time after the voltage supply system is started.

4. The power supply of claim 3, wherein

The delayed start unit includes:

a timer configured to detect that the predetermined period of time has elapsed after the voltage supply system is started,

an operation inhibiting unit configured to inhibit operation of the power supply in response to the fact that the voltage supply system is activated, an

An enabling unit configured to disable the operation prohibiting unit and enable power conversion in the power supply in response to a fact that the timer has detected that the predetermined period of time has elapsed.

5. The power supply of claim 4, wherein

The operation inhibiting unit includes a first current setting unit configured to set the current limit value to 0 in response to the fact that the voltage supply system is activated, and

the starting unit includes a second current setting unit configured to set the current limit value to a predetermined value greater than 0 in response to the fact that the timer has detected the elapse of a predetermined period of time.

6. The power supply of claim 5, wherein

The second current setting unit includes a limit value setting unit configured to set the current limit value to a value between a predetermined lower limit value and an upper limit value, the upper limit value being specified by a current value of the current supplied from the voltage supply system.

7. The power supply of claim 6, wherein

The limit value setting unit includes a current limit value determining unit configured to determine the current limit value as a value obtained by multiplying the current value of the current supplied from the voltage supply system by a value not less than 0 and less than 1.

8. The power supply of claim 6, wherein

The limit value setting unit includes a setting unit configured to set the current limit value such that a ratio of the current limit value to the current value of the current supplied from the voltage supply system becomes a predetermined target value equal to or greater than 0 and less than 1.

9. The power supply of claim 6, wherein

The second current setting unit includes:

a current value receiving unit configured to receive, from the constant voltage power supply, a value indicating a current value of a current output from the constant voltage power supply; and

a limit value setting unit configured to set the current limit value such that a ratio of the current limit value to a sum of the current value indicated by the value received by the current value receiving unit and a current value of the current output from the power supply becomes a predetermined target value that is not less than 0 and less than 1.

10. The power supply of claim 9, wherein

The limit setting unit includes:

a current value calculating unit configured to calculate the current value of the current output from the constant voltage power supply by a predetermined conversion expression with respect to the value received by the current value receiving unit, an

A current limiting unit configured to set the current limit value so that a ratio of the current limit value to a sum of the current value calculated by the current value calculating unit and the current value output by the power supply becomes the target value.

11. The power supply of claim 9 or 10, wherein

The target value is a ratio of a rated output current of the power supply to a sum of a rated output current of the constant voltage power supply and the rated output current of the power supply.

12. The power supply of any of claims 1-11, wherein

The second target voltage is a value not less than an upper limit of variation of the voltage output from the constant voltage power supply based on the first target voltage.

13. The power supply of claim 12, wherein

The second target voltage is a value equal to an upper limit of variation of the voltage output from the constant voltage power supply based on the first target voltage.

14. The power supply of claim 12 or 13, wherein

The variation is a value determined by the specification of the constant voltage power supply.

15. The power supply of claim 5, further comprising: a current value receiving unit configured to receive a signal indicating a current value of a current supplied from the voltage supply system, wherein

The second current setting unit includes a current limit value setting unit configured to set the current limit value to a value between a predetermined lower limit value and the current value indicated by the signal received by the current value receiving unit.

16. The power supply of claim 15, further comprising a current sensor configured to measure the current value of the current supplied to a load from the voltage supply system, wherein

The current value receiving unit receives a signal indicating the current value from the current sensor.

17. The power supply of claim 15, wherein

The voltage supply system further includes:

a current sensor configured to measure the current value of the current supplied from the voltage supply system to a load, an

A control unit configured to supply a signal indicating the current value measured by the current sensor to the current value receiving unit, and

the current value receiving unit receives the signal from the control unit.

18. The power supply of claim 5, further comprising: a current value receiving unit configured to receive a current value of a current output from the constant voltage power supply, wherein

The second current setting unit includes a current limit value setting unit configured to set the current limit value such that a ratio of the current limit value to the current value received by the current value receiving unit becomes a predetermined target value.

19. The power supply of claim 18, further comprising:

a current sensor configured to measure the current value of the current output from the constant voltage power supply; and

a control unit configured to supply a signal indicating the current value measured by the current sensor to the current value receiving unit, wherein

The current value receiving unit receives the signal from the control unit.

20. The power supply of claim 18, further comprising: a current sensor configured to measure the current value of the current output from the constant voltage power supply, wherein

The current value receiving unit receives the current value from the current sensor.

21. The power supply of claim 4, wherein

The operation inhibiting unit includes a drive signal stopping unit configured to stop outputting the drive signal to the voltage generating unit in response to a fact that the voltage supply system is activated, and

the start unit includes a drive signal output unit configured to start outputting the drive signal to the voltage generation unit in response to a fact that the timer has detected that the predetermined period of time has elapsed.

22. The power supply of claim 3, wherein

The delayed start unit includes:

a drive signal output stopping unit configured to stop outputting the drive signal to the voltage generating unit in response to the fact that the voltage supply system is activated, an

A start unit configured to start power conversion in the power supply by disabling the drive signal output stop unit in response to a fact that the timer detects that the predetermined period of time has elapsed.

23. The power supply of claim 2, wherein

The delay unit includes a delay start unit configured to start power conversion in the power supply in response to a fact that the power conversion in the constant voltage power supply is started.

24. The power supply of claim 23, wherein

The delay start unit starts power conversion in the power supply in response to at least one of a fact that the voltage output by the constant voltage power supply has reached the first target voltage and a fact that information indicating that power conversion is started is received from the constant voltage power supply.

25. The power supply according to any one of claims 1 to 24, further comprising a target voltage replacement unit configured to replace the second target voltage with a voltage output from the power supply in response to a fact that the voltage generation unit has started outputting the voltage in the constant current mode after the voltage supply system is started up.

26. The power supply of any of claims 1-25, further comprising:

a state detection unit configured to detect an operation state of the power supply; and

a limiting unit configured to limit an operation of the power supply in response to a fact that the state detecting unit has detected that the power supply is operating in the constant voltage mode.

27. The power supply of claim 26, wherein

The state detection unit detects whether the power supply is operating in the constant voltage mode based on whether the voltage output by the power supply has reached the second target voltage.

28. The power supply of claim 26, wherein

The limiting unit reduces the current limit to a value not less than 0 in response to the fact that the state detecting unit has detected that the power supply is operating in the constant voltage mode.

29. The power supply of any of claims 1-25, further comprising: a measurement unit configured to measure an output current of the power supply, wherein

30. The power supply of any of claims 1-29, further comprising: a determination unit configured to determine whether the constant voltage power supply is stopped, wherein

In response to the fact that the determination unit has determined that the constant voltage power supply is stopped, the second target voltage is replaced with the first target voltage, and the current limit is replaced with a rated maximum current value of the power supply.

31. The power supply of any of claims 1-30, wherein

The constant voltage power supply includes a direct current constant voltage power supply configured to output a direct current voltage in the constant voltage mode based on the first target voltage,

the power supply includes a direct-current voltage generating unit configured to switchably output a direct-current voltage between the constant-voltage mode and the constant-current mode.

32. The power supply of any of claims 1-30,

the constant voltage power supply includes an alternating current constant voltage power supply configured to output an alternating current voltage in the constant voltage mode based on the first target voltage,

the power supply includes an alternating voltage generating unit configured to switchably output an alternating voltage between the constant voltage mode and the constant current mode.

33. A voltage supply system comprising:

a first power supply configured to output a voltage in a constant voltage mode based on a first target voltage; and

The second power supply includes a voltage generation unit configured to switchably output a voltage between a constant voltage mode based on a second target voltage greater than the first target voltage and a constant current mode based on a current limit.